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_is1_defconfig b/configs/socfpga_is1_defconfig
index 371c630..9b9b929 100644
--- a/configs/socfpga_is1_defconfig
+++ b/configs/socfpga_is1_defconfig
@@ -35,6 +35,7 @@
 CONFIG_CMD_UBI=y
 CONFIG_SPL_DM=y
 CONFIG_SPL_DM_SEQ_ALIAS=y
+CONFIG_FPGA_SOCFPGA=y
 CONFIG_DM_GPIO=y
 CONFIG_DWAPB_GPIO=y
 CONFIG_SYS_I2C_DW=y