net: macb: Remove Microchip compatible string

Remove the microchip compatible string and default compatible "cdns,macb"
support both 32-bit and 64-bit DMA access.

Signed-off-by: Padmarao Begari <padmarao.begari@microchip.com>
Reviewed-by: Leo Yu-Chi Liang <ycliang@andestech.com>