pinctrl: amd: Add ACPI dependency

Currently the AMD pin controller driver supports ACPI platform only.
Make the PINCTRL_AMD config symbol depend on ACPI, to avoid asking the
user about it when configuring a kernel without ACPI support.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20200507113751.24213-1-geert+renesas@glider.be


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