FPGA: constify Lattice FPGA code

The Lattice code was missed by commit e6a857d "fpga: constify to fix
build warning" resulting in such warnings:

fpga.c: In function 'fpga_load':
fpga.c:238: warning: passing argument 2 of 'lattice_load' discards qualifiers from pointer target type
fpga.c: In function 'fpga_dump':
fpga.c:278: warning: passing argument 2 of 'lattice_dump' discards qualifiers from pointer target type

Signed-off-by: Wolfgang Denk <wd@denx.de>
cc: Stefano Babic <sbabic@denx.de>

drivers/fpga/lattice.c

@@ -34,7 +34,7 @@
 #include <lattice.h>
 
 static lattice_board_specific_func *pfns;
-static char *fpga_image;
+static const char *fpga_image;
 static unsigned long read_bytes;
 static unsigned long bufsize;
 static unsigned short expectedCRC;
@@ -302,7 +302,7 @@ static int lattice_validate(Lattice_desc *desc, const char *fn)
 	return ret_val;
 }
 
-int lattice_load(Lattice_desc *desc, void *buf, size_t bsize)
+int lattice_load(Lattice_desc *desc, const void *buf, size_t bsize)
 {
 	int ret_val = FPGA_FAIL;
 
@@ -335,7 +335,7 @@ int lattice_load(Lattice_desc *desc, void *buf, size_t bsize)
 	return ret_val;
 }
 
-int lattice_dump(Lattice_desc *desc, void *buf, size_t bsize)
+int lattice_dump(Lattice_desc *desc, const void *buf, size_t bsize)
 {
 	puts("Dump not supported for Lattice FPGA\n");
 

include/lattice.h

@@ -302,8 +302,8 @@ void sclock(void);
 void ispVMDelay(unsigned short int a_usMicroSecondDelay);
 void calibration(void);
 
-int lattice_load(Lattice_desc *desc, void *buf, size_t bsize);
-int lattice_dump(Lattice_desc *desc, void *buf, size_t bsize);
+int lattice_load(Lattice_desc *desc, const void *buf, size_t bsize);
+int lattice_dump(Lattice_desc *desc, const void *buf, size_t bsize);
 int lattice_info(Lattice_desc *desc);
 
 void ispVMStart(void);