ARM: clps711x: mark clps711x_compat as const

The array of string pointers is put in __initconst, and the strings themselves
are marke 'const' but the the pointers are not, which caused a warning when
built with LTO:

arch/arm/mach-clps711x/board-dt.c:72:20: error: 'clps711x_compat' causes a section type conflict with 'feroceon_ids'
 static const char *clps711x_compat[] __initconst = {

This marks the array itself const as well, which was certainly the
intention originally.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

arch/arm/mach-clps711x/board-dt.c

@@ -69,7 +69,7 @@ static void clps711x_restart(enum reboot_mode mode, const char *cmd)
 	soft_restart(0);
 }
 
-static const char *clps711x_compat[] __initconst = {
+static const char *const clps711x_compat[] __initconst = {
 	"cirrus,ep7209",
 	NULL
 };