net: macb: add polarfire soc reset support

To date, the Microchip PolarFire SoC (MPFS) has been using the
cdns,macb compatible, however the generic device does not have reset
support. Add a new compatible & .data for MPFS to hook into the reset
functionality added for zynqmp support (and make the zynqmp init
function generic in the process).

Reviewed-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>