pinctrl: add CONFIG_OF dependencies for microchip drivers

The two newly added drivers fail to link on builds without
CONFIG_OF:

x86_64-linux-ld: drivers/pinctrl/pinctrl-pic64gx-gpio2.o: in function `pinconf_generic_dt_node_to_map_all':
pinctrl-pic64gx-gpio2.c:(.text+0xc9): undefined reference to `pinconf_generic_dt_node_to_map'
x86_64-linux-ld: drivers/pinctrl/pinctrl-mpfs-iomux0.o: in function `pinconf_generic_dt_node_to_map_all':
pinctrl-mpfs-iomux0.c:(.text+0xc9): undefined reference to `pinconf_generic_dt_node_to_map'

Add a Kconfig dependencies.

Fixes: 38cf9d641314 ("pinctrl: add pic64gx "gpio2" pinmux driver")
Fixes: 46397274da22 ("pinctrl: add polarfire soc iomux0 pinmux driver")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Linus Walleij <linusw@kernel.org>