fpga: add definition for Xilinx Spartan-6 XC6SLX4

Signed-off-by: Stefano Babic <sbabic@denx.de>

include/spartan3.h

@@ -80,6 +80,12 @@ typedef struct {
 #define	XILINX_XC3S1200E_SIZE	3841184/8
 #define	XILINX_XC3S1600E_SIZE	5969696/8
 
+/*
+ * Spartan-6 : the Spartan-6 family can be programmed
+ * exactly as the Spartan-3
+ */
+#define XILINK_XC6SLX4_SIZE	(3713568/8)
+
 /* Descriptor Macros
  *********************************************************************/
 /* Spartan-III devices */
@@ -123,4 +129,7 @@ typedef struct {
 #define XILINX_XC3S1600E_DESC(iface, fn_table, cookie) \
 { Xilinx_Spartan3, iface, XILINX_XC3S1600E_SIZE, fn_table, cookie }
 
+#define XILINX_XC6SLX4_DESC(iface, fn_table, cookie) \
+{ Xilinx_Spartan3, iface, XILINK_XC6SLX4_SIZE, fn_table, cookie }
+
 #endif /* _SPARTAN3_H_ */