fpga: constify to fix build warning

Fix compiler warning:

cmd_fpga.c:318: warning: passing argument 3 of 'fit_image_get_data'
from incompatible pointer type

Adding the needed 'const' here entails a whole bunch of additonal
changes all over the FPGA code.

Signed-off-by: Wolfgang Denk <wd@denx.de>
Cc: Andre Schwarz <andre.schwarz@matrix-vision.de>
Cc: Murray Jensen <Murray.Jensen@csiro.au>
Acked-by: Andre Schwarz<andre.schwarz@matrix-vision.de>
diff --git a/drivers/fpga/fpga.c b/drivers/fpga/fpga.c
index a669039..26d2443 100644
--- a/drivers/fpga/fpga.c
+++ b/drivers/fpga/fpga.c
@@ -52,7 +52,7 @@
 
 /* Local static functions */
 static __attribute__((__const__)) fpga_desc * __attribute__((__const__)) fpga_get_desc( int devnum );
-static __attribute__((__const__)) fpga_desc * __attribute__((__const__)) fpga_validate( int devnum, void *buf,
+static __attribute__((__const__)) fpga_desc * __attribute__((__const__)) fpga_validate(int devnum, const void *buf,
 					 size_t bsize, char *fn );
 static int fpga_dev_info( int devnum );
 
@@ -94,7 +94,7 @@
 /* fpga_validate
  *	generic parameter checking code
  */
-static __attribute__((__const__)) fpga_desc * __attribute__((__const__)) fpga_validate( int devnum, void *buf,
+static __attribute__((__const__)) fpga_desc * __attribute__((__const__)) fpga_validate(int devnum, const void *buf,
 					 size_t bsize, char *fn )
 {
 	fpga_desc * desc = fpga_get_desc( devnum );
@@ -212,7 +212,7 @@
 /*
  *	Generic multiplexing code
  */
-int fpga_load( int devnum, void *buf, size_t bsize )
+int fpga_load(int devnum, const void *buf, size_t bsize)
 {
 	int ret_val = FPGA_FAIL;           /* assume failure */
 	fpga_desc * desc = fpga_validate( devnum, buf, bsize, (char *)__FUNCTION__ );
@@ -252,7 +252,7 @@
 /* fpga_dump
  *	generic multiplexing code
  */
-int fpga_dump( int devnum, void *buf, size_t bsize )
+int fpga_dump(int devnum, const void *buf, size_t bsize)
 {
 	int ret_val = FPGA_FAIL;           /* assume failure */
 	fpga_desc * desc = fpga_validate( devnum, buf, bsize, (char *)__FUNCTION__ );