net: gem: Move gem to Kconfig

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Reviewed-by: Jagan Teki <jteki@openedev.com>
diff --git a/configs/zynq_zc702_defconfig b/configs/zynq_zc702_defconfig
index 8318b94..dd588af 100644
--- a/configs/zynq_zc702_defconfig
+++ b/configs/zynq_zc702_defconfig
@@ -15,4 +15,5 @@
 CONFIG_SPI_FLASH_STMICRO=y
 CONFIG_SPI_FLASH_WINBOND=y
 CONFIG_PHYLIB=y
+CONFIG_ZYNQ_GEM=y
 CONFIG_ZYNQ_QSPI=y