gpio: omap: Fix missing raw locks conversion

Fix below build warning:
  CC      drivers/gpio/gpio-omap.o
drivers/gpio/gpio-omap.c: In function 'omap_gpio_irq_type':
drivers/gpio/gpio-omap.c:504:3: warning: passing argument 1 of 'spin_unlock_irqrestore' from incompatible pointer type [enabled by default]
include/linux/spinlock.h:360:29: note: expected 'struct spinlock_t *' but argument is of type 'struct raw_spinlock_t *'

Fixes: commit 4dbada2b ("gpio: omap: use raw locks for locking")
Signed-off-by: Axel Lin <axel.lin@ingics.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>