arm: drop volatile qualifier from gd pointer

There's a bunch of other places where this qualifier should be
dropped, e.g. in the set_gd() prototype and for various variables used
for stashing the value in the mach-imx/ directory and elsewhere. But
that will be done in follow-up patches.

Signed-off-by: Rasmus Villemoes <ravi@prevas.dk>
Tested-by: Anshul Dalal <anshuld@ti.com>

arch/arm/include/asm/global_data.h

@@ -133,9 +133,9 @@ static inline gd_t *get_gd(void)
 #else
 
 #ifdef CONFIG_ARM64
-#define DECLARE_GLOBAL_DATA_PTR		register volatile gd_t *gd asm ("x18")
+#define DECLARE_GLOBAL_DATA_PTR		register gd_t *gd asm ("x18")
 #else
-#define DECLARE_GLOBAL_DATA_PTR		register volatile gd_t *gd asm ("r9")
+#define DECLARE_GLOBAL_DATA_PTR		register gd_t *gd asm ("r9")
 #endif
 #endif