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/include/ACEX1K.h b/include/ACEX1K.h
index 2bb9226..e2e96d2 100644
--- a/include/ACEX1K.h
+++ b/include/ACEX1K.h
@@ -30,13 +30,13 @@
 
 #include <altera.h>
 
-extern int ACEX1K_load( Altera_desc *desc, void *image, size_t size );
-extern int ACEX1K_dump( Altera_desc *desc, void *buf, size_t bsize );
-extern int ACEX1K_info( Altera_desc *desc );
+extern int ACEX1K_load(Altera_desc *desc, const void *image, size_t size);
+extern int ACEX1K_dump(Altera_desc *desc, const void *buf, size_t bsize);
+extern int ACEX1K_info(Altera_desc *desc);
 
-extern int CYC2_load( Altera_desc *desc, void *image, size_t size );
-extern int CYC2_dump( Altera_desc *desc, void *buf, size_t bsize );
-extern int CYC2_info( Altera_desc *desc );
+extern int CYC2_load(Altera_desc *desc, const void *image, size_t size);
+extern int CYC2_dump(Altera_desc *desc, const void *buf, size_t bsize);
+extern int CYC2_info(Altera_desc *desc);
 
 /* Slave Serial Implementation function table */
 typedef struct {