[efi] Disable receive filters to work around buggy UNDI drivers

[efi] Disable receive filters to work around buggy UNDI drivers

Some UNDI drivers (such as the AMI UsbNetworkPkg currently in the
process of being upstreamed into EDK2) have a bug that will prevent
any packets from being received unless at least one attempt has been
made to disable some receive filters.

Work around these buggy drivers by attempting to disable receive
filters before enabling them.  Ignore any errors, since we genuinely
do not care whether or not the disabling succeeds.

Signed-off-by: Michael Brown <mcb30@ipxe.org>