kconfig: Convert FPGA_SOCFPGA configuration to Kconfig

This converts the following to Kconfig:
   CONFIG_FPGA_SOCFPGA

Signed-off-by: Tien Fong Chee <tien.fong.chee@intel.com>
Reviewed-by: Ley Foon Tan <ley.foon.tan@intel.com>
Reviewed-by: Dinh Nguyen <dinguyen@kernel.org>
diff --git a/configs/socfpga_de0_nano_soc_defconfig b/configs/socfpga_de0_nano_soc_defconfig
index dabdb97..f56e45e 100644
--- a/configs/socfpga_de0_nano_soc_defconfig
+++ b/configs/socfpga_de0_nano_soc_defconfig
@@ -40,6 +40,7 @@
 CONFIG_CMD_UBI=y
 CONFIG_SPL_DM=y
 CONFIG_DFU_MMC=y
+CONFIG_FPGA_SOCFPGA=y
 CONFIG_DM_GPIO=y
 CONFIG_DWAPB_GPIO=y
 CONFIG_SYS_I2C_DW=y