pinctrl: imx: PINCTRL_IMX_SCMI should depend on ARCH_MXC

pinctrl: imx: PINCTRL_IMX_SCMI should depend on ARCH_MXC

i.MX95 SCMI firmware is only present on NXP i.MX94 and i.MX95 SoCs.
Hence add a dependency on ARCH_MXC, to prevent asking the user about
this driver when configuring a kernel without NXP i.MX SoC family
support.

While at it, relax the dependencies on ARM_SCMI_PROTOCOL and OF when
compile-testing.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Peng Fan <peng.fan@nxp.com>
Signed-off-by: Linus Walleij <linusw@kernel.org>