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/board/hymod/bsp.c b/board/hymod/bsp.c
index 9a929413..2cd3707 100644
--- a/board/hymod/bsp.c
+++ b/board/hymod/bsp.c
@@ -75,14 +75,14 @@
  */
 
 int
-fpga_load (int mezz, uchar *addr, ulong size)
+fpga_load(int mezz, const uchar *addr, ulong size)
 {
 	hymod_conf_t *cp = &gd->bd->bi_hymod_conf;
 	xlx_info_t *fp;
 	xlx_iopins_t *fpgaio;
 	volatile uchar *fpgabase;
 	volatile uint cnt;
-	uchar *eaddr = addr + size;
+	const uchar *eaddr = addr + size;
 	int result;
 
 	if (mezz)