arm: zynq: Enable FPGA/FPGA_XILINX via Kconfig

Enabling fpga via Kconfig.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
diff --git a/configs/zynq_zc770_xm013_defconfig b/configs/zynq_zc770_xm013_defconfig
index 39f6199..6d34b21 100644
--- a/configs/zynq_zc770_xm013_defconfig
+++ b/configs/zynq_zc770_xm013_defconfig
@@ -27,6 +27,7 @@
 CONFIG_CMD_CACHE=y
 CONFIG_NET_RANDOM_ETHADDR=y
 CONFIG_SPL_DM_SEQ_ALIAS=y
+CONFIG_FPGA_XILINX=y
 # CONFIG_MMC is not set
 CONFIG_SPI_FLASH=y
 CONFIG_SPI_FLASH_BAR=y