rmnet: initialize rmnet pid ht spinlock

Initializes the rmnet ht spinlock to avoid a watchdog bite when
spinlock debugging is enabled. Fixes the following:
3.062142:   <6> spinlock bad magic on CPU#5
3.062154:   <6>  lock: rmnet_pid_ht_splock+0x0/0x18, .magic: 00000000
3.062156:   <4> Causing a watchdog bite.

Change-Id: I2e87b08bf00ba1b77445b2164db58da9ab6d559b
Signed-off-by: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>