net: Kconfig: FEC: Add dependency on i.MX8M

Make FEC driver could be used by i.MX8M when CONFIG_FEC_MXC defined
in defconfig.
Signed-off-by: NPeng Fan <peng.fan@nxp.com>
Reviewed-by: NFrieder Schrempf <frieder.schrempf@kontron.de>
Tested-by: NFrieder Schrempf <frieder.schrempf@kontron.de>

drivers/net/Kconfig

@@ -236,7 +236,7 @@ config FEC_MXC_MDIO_BASE
 
 config FEC_MXC
 	bool "FEC Ethernet controller"
-	depends on MX28 || MX5 || MX6 || MX7 || IMX8 || VF610
+	depends on MX28 || MX5 || MX6 || MX7 || IMX8 || IMX8M || VF610
 	help
 	  This driver supports the 10/100 Fast Ethernet controller for
 	  NXP i.MX processors.