phy: intel: PHY_INTEL_KEEMBAY_EMMC should depend on ARCH_KEEMBAY

phy: intel: PHY_INTEL_KEEMBAY_EMMC should depend on ARCH_KEEMBAY

The Intel Keem Bay eMMC PHY is only present on Intel Keem Bay SoCs.
Hence add a dependency on ARCH_KEEMBAY, to prevent asking the user about
this driver when configuring a kernel without Intel Keem Bay platform
support.

Fixes: 885c4f4d6cf448f6 ("phy: intel: Add Keem Bay eMMC PHY support")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20201110144600.3279752-1-geert+renesas@glider.be
Signed-off-by: Vinod Koul <vkoul@kernel.org>