pinctrl: freescale: Use CONFIG_SOC_IMXRT to guard i.MX RT1xxx drivers

This aligns with the use of SOC_IMX* as dependencies for all the other
mach-imx pinctrl drivers. Enabling i.MX RT pinctrl drivers for a kernel
with out i.MX RT SOC support is pointless.

Signed-off-by: Esben Haabendal <esben@geanix.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/20240506-imx-pinctrl-optional-v2-2-bdff75085156@geanix.com


Signed-off-by: Linus Walleij <linus.walleij@linaro.org>