net: gem: Move gem to Kconfig

configs/xilinx_zynqmp_ep_defconfig

configs/zynq_microzed_defconfig

configs/zynq_picozed_defconfig

configs/zynq_zc702_defconfig

configs/zynq_zc706_defconfig

configs/zynq_zc770_xm010_defconfig

configs/zynq_zc770_xm011_defconfig

configs/zynq_zc770_xm012_defconfig

configs/zynq_zc770_xm013_defconfig

configs/zynq_zed_defconfig

configs/zynq_zybo_defconfig

drivers/net/Kconfig

include/configs/xilinx_zynqmp.h

include/configs/xilinx_zynqmp_ep.h

include/configs/zynq-common.h

include/configs/zynq_microzed.h

include/configs/zynq_picozed.h

include/configs/zynq_zc70x.h

include/configs/zynq_zc770.h

include/configs/zynq_zed.h