net: mdio: MDIO_PIC64HPSC should depend on ARCH_MICROCHIP

net: mdio: MDIO_PIC64HPSC should depend on ARCH_MICROCHIP

The PIC64-HPSC/HX MDIO interface is only present on Microchip
PIC64-HPSC/HX SoCs.  Hence add a dependency on ARCH_MICROCHIP, to
prevent asking the user about this driver when configuring a kernel
without Microchip SoC support.

Fixes: f76aef980206e7c6 ("net: mdio: add a driver for PIC64-HPSC/HX MDIO controller")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Charles Perry <charles.perry@microchip.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/980c57efa5843733ef95459c3283aebade56f142.1776162544.git.geert+renesas@glider.be
Signed-off-by: Jakub Kicinski <kuba@kernel.org>