hwmon: qpnp-adc: Initialize adc mutex in each driver

The qpnp adc drivers take different mutex locks one after the
other but lockdep can't figure that out because each mutex is
intialized with one call to mutex_init() in
qpnp_adc_get_devicetree_data(). Move the mutex initialization to
each caller so that lockdep can see different lock classes for
each adc mutex. This silences the below recursive mutex warning.

=============================================
[ INFO: possible recursive locking detected ]
3.4.0-gc11e688-00030-g8f5e269-dirty #567 Tainted: G        W
---------------------------------------------
kworker/u:2/21 is trying to acquire lock:
 (&adc_qpnp->adc_lock){+.+...}, at: [<c04c0918>] qpnp_iadc_read+0x64/0x174

but task is already holding lock:
 (&adc_qpnp->adc_lock){+.+...}, at: [<c04be7f4>] qpnp_vadc_iadc_sync_request+0x34/0x198

other info that might help us debug this:
 Possible unsafe locking scenario:

       CPU0
       ----
  lock(&adc_qpnp->adc_lock);
  lock(&adc_qpnp->adc_lock);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

6 locks held by kworker/u:2/21:
 #0:  (deferwq){.+.+.+}, at: [<c00a7e84>] process_one_work+0x1c8/0x528
 #1:  (deferred_probe_work){+.+.+.}, at: [<c00a7e84>] process_one_work+0x1c8/0x528
 #2:  (&__lockdep_no_validate__){......}, at: [<c0339670>] device_attach+0x18/0xa4
 #3:  (&chip->last_ocv_uv_mutex){+.+...}, at: [<c04b8b74>] recalculate_soc+0x190/0x124c
 #4:  (&iadc->iadc_vadc_lock){+.+...}, at: [<c04c0aa8>] qpnp_iadc_vadc_sync_read+0x40/0xe4
 #5:  (&adc_qpnp->adc_lock){+.+...}, at: [<c04be7f4>] qpnp_vadc_iadc_sync_request+0x34/0x198

stack backtrace:
[<c00140cc>] (unwind_backtrace+0x0/0x11c) from [<c00d6ea8>] (__lock_acquire+0x238/0x1784)
[<c00d6ea8>] (__lock_acquire+0x238/0x1784) from [<c00d895c>] (lock_acquire+0xf0/0x138)
[<c00d895c>] (lock_acquire+0xf0/0x138) from [<c079aa50>] (mutex_lock_nested+0x5c/0x3d8)
[<c079aa50>] (mutex_lock_nested+0x5c/0x3d8) from [<c04c0918>] (qpnp_iadc_read+0x64/0x174)
[<c04c0918>] (qpnp_iadc_read+0x64/0x174) from [<c04c0ae0>] (qpnp_iadc_vadc_sync_read+0x78/0xe4)
[<c04c0ae0>] (qpnp_iadc_vadc_sync_read+0x78/0xe4) from [<c04b6d88>] (get_simultaneous_batt_v_and_i+0x24/0x68)
[<c04b6d88>] (get_simultaneous_batt_v_and_i+0x24/0x68) from [<c04b927c>] (recalculate_soc+0x898/0x124c)
[<c04b927c>] (recalculate_soc+0x898/0x124c) from [<c04b9cfc>] (calculate_soc_work+0x10/0x4c)
[<c04b9cfc>] (calculate_soc_work+0x10/0x4c) from [<c07750f8>] (qpnp_bms_probe+0xeac/0x1228)
[<c07750f8>] (qpnp_bms_probe+0xeac/0x1228) from [<c037d6b0>] (spmi_drv_probe+0x10/0x14)
[<c037d6b0>] (spmi_drv_probe+0x10/0x14) from [<c0339884>] (driver_probe_device+0x134/0x338)
[<c0339884>] (driver_probe_device+0x134/0x338) from [<c0337d28>] (bus_for_each_drv+0x48/0x8c)
[<c0337d28>] (bus_for_each_drv+0x48/0x8c) from [<c03396d8>] (device_attach+0x80/0xa4)
[<c03396d8>] (device_attach+0x80/0xa4) from [<c0338bdc>] (bus_probe_device+0x28/0x9c)
[<c0338bdc>] (bus_probe_device+0x28/0x9c) from [<c0339144>] (deferred_probe_work_func+0x68/0xa0)
[<c0339144>] (deferred_probe_work_func+0x68/0xa0) from [<c00a7f54>] (process_one_work+0x298/0x528)
[<c00a7f54>] (process_one_work+0x298/0x528) from [<c00a83a8>] (worker_thread+0x198/0x2b8)
[<c00a83a8>] (worker_thread+0x198/0x2b8) from [<c00ad2fc>] (kthread+0x90/0xa4)
[<c00ad2fc>] (kthread+0x90/0xa4) from [<c000edcc>] (kernel_thread_exit+0x0/0x8)

Change-Id: Iebda9a8dfc407273748545bb81f91d6dc27e97cc
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>