Silicon/Broadcom/BcmGenetDxe: program MAC also when not connected

In preparation of removing the EfiBootManagerConnectAll() from the
ordinary boot path, ensure that the MAC programming of the GENET
occurs even if the SNP driver for it is never invoked by the BDS.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@arm.com>
Reviewed-by: Pete Batard <pete@akeo.ie>
Tested-by: Pete Batard <pete@akeo.ie>
Acked-by: Leif Lindholm <leif@nuviainc.com>