fsl/fman_port: remove redundant check on port->rev_info.major

The check port->rev_info.major >= 6 is being performed twice, thus
the inner second check is always true and is redundant, hence it
can be removed. Detected by cppcheck.

drivers/net/ethernet/freescale/fman/fman_port.c:1394]: (warning)
Identical inner 'if' condition is always true.

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: David S. Miller <davem@davemloft.net>