fbdev: Constify struct sbus_mmap_map

'struct sbus_mmap_map' are not modified in these drivers.

Constifying this structure moves some data to a read-only section, so
increases overall security.

Update sbusfb_mmap_helper() accordingly.

On a x86_64, with allmodconfig, as an example:
Before:
======
text data bss dec hex filename
2452 536 16 3004 bbc drivers/video/fbdev/bw2.o

After:
=====
text data bss dec hex filename
2500 483 16 2999 bb7 drivers/video/fbdev/bw2.o

Signed-off-by: Christophe JAILLET <[e-mail]>
Signed-off-by: Helge Deller <[e-mail]>

drivers/video/fbdev/bw2.c

···
 	return 0;
 }
 
-static struct sbus_mmap_map bw2_mmap_map[] = {
+static const struct sbus_mmap_map bw2_mmap_map[] = {
 	{
 		.size = SBUS_MMAP_FBSIZE(1)
 	},

drivers/video/fbdev/cg14.c

···
 	info->fix.accel = FB_ACCEL_SUN_CG14;
 }
 
-static struct sbus_mmap_map __cg14_mmap_map[CG14_MMAP_ENTRIES] = {
+static const struct sbus_mmap_map __cg14_mmap_map[CG14_MMAP_ENTRIES] = {
 	{
 		.voff	= CG14_REGS,
 		.poff	= 0x80000000,

drivers/video/fbdev/cg3.c

···
 	return 0;
 }
 
-static struct sbus_mmap_map cg3_mmap_map[] = {
+static const struct sbus_mmap_map cg3_mmap_map[] = {
 	{
 		.voff	= CG3_MMAP_OFFSET,
 		.poff	= CG3_RAM_OFFSET,

drivers/video/fbdev/cg6.c

···
 	return 0;
 }
 
-static struct sbus_mmap_map cg6_mmap_map[] = {
+static const struct sbus_mmap_map cg6_mmap_map[] = {
 	{
 		.voff	= CG6_FBC,
 		.poff	= CG6_FBC_OFFSET,

drivers/video/fbdev/ffb.c

···
 	return 0;
 }
 
-static struct sbus_mmap_map ffb_mmap_map[] = {
+static const struct sbus_mmap_map ffb_mmap_map[] = {
 	{
 		.voff	= FFB_SFB8R_VOFF,
 		.poff	= FFB_SFB8R_POFF,

drivers/video/fbdev/leo.c

···
 	return 0;
 }
 
-static struct sbus_mmap_map leo_mmap_map[] = {
+static const struct sbus_mmap_map leo_mmap_map[] = {
 	{
 		.voff	= LEO_SS0_MAP,
 		.poff	= LEO_OFF_SS0,

drivers/video/fbdev/p9100.c

···
 	return 0;
 }
 
-static struct sbus_mmap_map p9100_mmap_map[] = {
+static const struct sbus_mmap_map p9100_mmap_map[] = {
 	{ CG3_MMAP_OFFSET,	0,		SBUS_MMAP_FBSIZE(1) },
 	{ 0,			0,		0		    }
 };

drivers/video/fbdev/sbuslib.c

···
 	return fbsize * (-size);
 }
 
-int sbusfb_mmap_helper(struct sbus_mmap_map *map,
+int sbusfb_mmap_helper(const struct sbus_mmap_map *map,
 		       unsigned long physbase,
 		       unsigned long fbsize,
 		       unsigned long iospace,

drivers/video/fbdev/sbuslib.h

···
 
 extern void sbusfb_fill_var(struct fb_var_screeninfo *var,
 			    struct device_node *dp, int bpp);
-extern int sbusfb_mmap_helper(struct sbus_mmap_map *map,
+extern int sbusfb_mmap_helper(const struct sbus_mmap_map *map,
 			      unsigned long physbase, unsigned long fbsize,
 			      unsigned long iospace,
 			      struct vm_area_struct *vma);

drivers/video/fbdev/tcx.c

···
 	return 0;
 }
 
-static struct sbus_mmap_map __tcx_mmap_map[TCX_MMAP_ENTRIES] = {
+static const struct sbus_mmap_map __tcx_mmap_map[TCX_MMAP_ENTRIES] = {
 	{
 		.voff	= TCX_RAM8BIT,
 		.size	= SBUS_MMAP_FBSIZE(1)