gpio: rockchip: needs GENERIC_IRQ_CHIP to fix build errors

gpio-rockchip uses interfaces that are provided by the Kconfig
symbol GENERIC_IRQ_CHIP, so the driver should select that symbol
in order to prevent build errors.

Fixes these build errors (and more):

aarch64-linux-ld: drivers/gpio/gpio-rockchip.o: in function `rockchip_irq_disable':
gpio-rockchip.c:(.text+0x454): undefined reference to `irq_gc_mask_set_bit'
aarch64-linux-ld: drivers/gpio/gpio-rockchip.o: in function `rockchip_irq_enable':
gpio-rockchip.c:(.text+0x478): undefined reference to `irq_gc_mask_clr_bit'
aarch64-linux-ld: drivers/gpio/gpio-rockchip.o: in function `rockchip_interrupts_register':
gpio-rockchip.c:(.text+0x518): undefined reference to `irq_generic_chip_ops'
aarch64-linux-ld: gpio-rockchip.c:(.text+0x594): undefined reference to `__irq_alloc_domain_generic_chips'
aarch64-linux-ld: gpio-rockchip.c:(.text+0x5cc): undefined reference to `irq_get_domain_generic_chip'
aarch64-linux-ld: gpio-rockchip.c:(.text+0x5e0): undefined reference to `irq_gc_ack_set_bit'
aarch64-linux-ld: gpio-rockchip.c:(.text+0x604): undefined reference to `irq_gc_set_wake'

Fixes: 936ee267

 ("gpio/rockchip: add driver for rockchip gpio")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>