usb: musb: only cancel work if it is initialized

Since commit c5340bd1 ("usb: musb: cancel work on removal") the workqueue
is cancelled but then if we bail out before the workqueue is setup we
get this:

|INFO: trying to register non-static key.
|the code is fine but needs lockdep annotation.
|turning off the locking correctness validator.
|CPU: 0 PID: 708 Comm: modprobe Not tainted 3.12.0+ #435
|[<c00867bc>] (lock_acquire+0xf0/0x108) from [<c00529d0>] (flush_work+0x38/0x2ec)
|[<c00529d0>] (flush_work+0x38/0x2ec) from [<c0052d24>] (__cancel_work_timer+0xa0/0x134)
|[<c0052d24>] (__cancel_work_timer+0xa0/0x134) from [<bf0e4ae4>] (musb_free+0x40/0x60 [musb_hdrc])
|[<bf0e4ae4>] (musb_free+0x40/0x60 [musb_hdrc]) from [<bf0e5364>] (musb_probe+0x678/0xb78 [musb_hdrc])
|[<bf0e5364>] (musb_probe+0x678/0xb78 [musb_hdrc]) from [<c0294bf0>] (platform_drv_probe+0x1c/0x24)
|[<c0294bf0>] (platform_drv_probe+0x1c/0x24) from [<c0293970>] (driver_probe_device+0x90/0x224)
|[<c0293970>] (driver_probe_device+0x90/0x224) from [<c0291ef0>] (bus_for_each_drv+0x60/0x8c)
|[<c0291ef0>] (bus_for_each_drv+0x60/0x8c) from [<c02938bc>] (device_attach+0x80/0xa4)
|[<c02938bc>] (device_attach+0x80/0xa4) from [<c0292b24>] (bus_probe_device+0x88/0xac)
|[<c0292b24>] (bus_probe_device+0x88/0xac) from [<c0291490>] (device_add+0x388/0x6c8)
|[<c0291490>] (device_add+0x388/0x6c8) from [<c02952a0>] (platform_device_add+0x188/0x22c)
|[<c02952a0>] (platform_device_add+0x188/0x22c) from [<bf11ea30>] (dsps_probe+0x294/0x394 [musb_dsps])
|[<bf11ea30>] (dsps_probe+0x294/0x394 [musb_dsps]) from [<c0294bf0>] (platform_drv_probe+0x1c/0x24)
|platform musb-hdrc.1.auto: Driver musb-hdrc requests probe deferral
|musb-hdrc musb-hdrc.1.auto: musb_init_controller failed with status -517

This patch moves the init part to earlier part so it can be cleaned as
part of the fail3 label because now it is surrounded by the fail4 label.
Step two is to remove it from musb_free() and add it to the two cleanup
paths (error path and device removal) separately.

Cc: stable@vger.kernel.org
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Felipe Balbi <balbi@ti.com>