usb: gadget: mv_udc_core: fix sparse warnings

fix the following sparse warnings:

drivers/usb/gadget/mv_udc_core.c:1850:6: warning: symbol 'irq_process_reset' was not declared. Should it be static?
drivers/usb/gadget/mv_udc_core.c:247:9: warning: context imbalance in 'done' - unexpected unlock
drivers/usb/gadget/mv_udc_core.c:1692:25: warning: context imbalance in 'handle_setup_packet' - unexpected unlock

Note that there are still other sparse warnings
which aren't trivial to fix, so I left them out:

drivers/usb/gadget/mv_udc_core.c:848:34: warning: incorrect type in argument 1 (different address spaces)
drivers/usb/gadget/mv_udc_core.c:848:34:    expected void const volatile [noderef] <asn:2>*addr
drivers/usb/gadget/mv_udc_core.c:848:34:    got unsigned int *<noident>
drivers/usb/gadget/mv_udc_core.c:849:42: warning: incorrect type in argument 2 (different address spaces)
drivers/usb/gadget/mv_udc_core.c:849:42:    expected void volatile [noderef] <asn:2>*addr
drivers/usb/gadget/mv_udc_core.c:849:42:    got unsigned int *<noident>

Acked-by: Neil Zhang <zhangwm@marvell.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>