usb: gadget: serial: resolve spinlock inconsistencies
usb: gadget: serial: resolve spinlock inconsistencies

kernel throws Possbile dead lock at f_serial  completion handlers,
if we use plain spinlock which dont disables interrupts.
To avoid this use spinlock_irqsave instead of plain spinlock
which disables interrupts.

Signed-off-by: Anji Jonnala <d32984257c2b1f19a52887b31db69164a662fd03@qualcomm.com>

TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas