fpga: Added Kconfig support for FPGA_SPARTAN3

This patch added Kconfig support for FPGA_SPARTAN3 and migrates the
values over to the defconfigs.

Signed-off-by: Vipul Kumar <vipulk@xilinx.com>
Signed-off-by: Siva Durga Prasad Paladugu <sivadur@xilinx.com>
diff --git a/drivers/fpga/Kconfig b/drivers/fpga/Kconfig
index 6b2c866..4f9f0d1 100644
--- a/drivers/fpga/Kconfig
+++ b/drivers/fpga/Kconfig
@@ -45,4 +45,9 @@
 	  Enable FPGA driver for loading bitstream in BIT and BIN format
 	  on Xilinx Zynq UltraScale+ (ZynqMP) device.
 
+config FPGA_SPARTAN3
+       bool "Enable Spartan3 FPGA driver"
+       help
+         Enable Spartan3 FPGA driver for loading in BIT format.
+
 endmenu