pinctrl: zynq: add CONFIG_OF dependency

The zynq driver can be enabled for compile-testing on builds without
CONFIG_OF, leading to a link error:

ld.lld-21: error: undefined symbol: pinconf_generic_dt_node_to_map
referenced by pinconf-generic.h:231 (/home/arnd/arm-soc/include/linux/pinctrl/pinconf-generic.h:231)
drivers/pinctrl/pinctrl-zynq.o:(pinconf_generic_dt_node_to_map_all) in archive vmlinux.a

Prevent this with the proper compile time dependency.

Reported-by: kernel test robot <[e-mail]>
Closes: https://lore.kernel.org/oe-kbuild-all/[e-mail]/
Fixes: 1982621decaf ("pinctrl: Allow compile testing for K210, TB10X and ZYNQ")
Signed-off-by: Arnd Bergmann <[e-mail]>
Link: https://lore.kernel.org/[e-mail]
Signed-off-by: Linus Walleij <[e-mail]>

drivers/pinctrl/Kconfig

···
 config PINCTRL_ZYNQ
 	bool "Pinctrl driver for Xilinx Zynq"
 	depends on ARCH_ZYNQ || COMPILE_TEST
+	depends on OF
 	select PINMUX
 	select GENERIC_PINCONF
 	help