pinctrl: imx8m: kconfig: Fix build error on test compile

pinctrl: imx8m: kconfig: Fix build error on test compile

PINCTRL_IMX depends on OF, however the dependency is missed when selected
by PINCTRL_IMX8M* (it does not follow the indirect 'select' statements),
select it explicitly.

Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Linus Walleij <linus.walleij@linaro.org>
Reported-by: kernel test robot <lkp@intel.com>
Link: https://lore.kernel.org/all/202209050605.fezJUgFH-lkp@intel.com/
Fixes: 87c2a29a6bf1 ("pinctrl: imx8m: kconfig: Depends on SOC_IMX8M")
Signed-off-by: Francesco Dolcini <francesco.dolcini@toradex.com>
Reviewed-by: Jacky Bai <ping.bai@nxp.com>
Link: https://lore.kernel.org/r/20220905224408.346425-1-francesco.dolcini@toradex.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>