drivers: net: xgene: Fix compiler warnings

Fixed compiler warnings reported with -Wmaybe-uninitialized W=1,

      /drivers/net/ethernet/apm/xgene/xgene_enet_main.c: In function ‘xgene_enet_rx_frame’:
      ../drivers/net/ethernet/apm/xgene/xgene_enet_main.c:455:27: warning: variable ‘pdata’ set but not used [-Wunused-but-set-variable]
      struct xgene_enet_pdata *pdata;
      ^
      ../drivers/net/ethernet/apm/xgene/xgene_enet_main.c: In function ‘xgene_enet_remove’:
      ../drivers/net/ethernet/apm/xgene/xgene_enet_main.c:1691:30: warning: variable ‘mac_ops’ set but not used [-Wunused-but-set-variable]
      const struct xgene_mac_ops *mac_ops;
				                                   ^

Signed-off-by: Iyappan Subramanian <isubramanian@apm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>