MLK-16221-6 usb: cdns3: gadget: fix non-initialized spinlock warning

MLK-16221-6 usb: cdns3: gadget: fix non-initialized spinlock warning

The below warning is showed if we open lockdep debug, fix it by
initializing spinlock before using it.

[  192.159535] INFO: trying to register non-static key.
[  192.164507] the code is fine but needs lockdep annotation.
[  192.169996] turning off the locking correctness validator.
[  192.175485] CPU: 1 PID: 2831 Comm: modprobe Not tainted 4.9.11-03045-g39aab30 #514
[  192.183054] Hardware name: Freescale i.MX8QXP LPDDR4 ARM2 (DT)
[  192.188884] Call trace:
[  192.191348] [<ffff200008089234>] dump_backtrace+0x0/0x1e0
[  192.196751] [<ffff200008089428>] show_stack+0x14/0x1c
[  192.201808] [<ffff2000084046f4>] dump_stack+0xb0/0xec
[  192.206865] [<ffff200008107570>] register_lock_class+0x510/0x538
[  192.212873] [<ffff20000810b7c4>] __lock_acquire+0x84/0x6f0
[  192.218363] [<ffff20000810c34c>] lock_acquire+0x68/0xc8
[  192.223596] [<ffff200008bfe1f4>] _raw_spin_lock_irqsave+0x50/0x68
[  192.229694] [<ffff200008857528>] usb_ss_gadget_udc_start+0x38/0x1b0
[  192.235966] [<ffff20000889da8c>] udc_bind_to_driver+0xcc/0x11c
[  192.241803] [<ffff20000889e0e4>] usb_gadget_probe_driver+0xa4/0x150
[  192.248077] [<ffff2000088983a8>] usb_composite_probe+0xb8/0xd8
[  192.253923] [<ffff200000ce8018>] msg_init+0x18/0x1000 [g_mass_storage]
[  192.260456] [<ffff200008083960>] do_one_initcall+0x38/0x12c
[  192.266033] [<ffff200008187764>] do_init_module+0x98/0x214
[  192.271523] [<ffff2000081465fc>] load_module+0x1014/0x10f0
[  192.277012] [<ffff200008146970>] SyS_finit_module+0xc8/0xd4
[  192.282590] [<ffff20000808374c>] __sys_trace_return+0x0/0x4

Signed-off-by: Peter Chen <peter.chen@nxp.com>