ARM: prevent compiler warnings from bootm.c

Without preceding declarations, "make C=1" generates
"Should it be static?" warnings for symbols
	do_bootm_linux,
	boot_prep_vxworks, and
	boot_jump_vxworks

Include of bootm.h also identified a signature mismatch
(const on argv[]).

Signed-off-by: Eric Nelson <eric.nelson@boundarydevices.com>
Acked-by: Albert ARIBAUD <albert.u.boot@aribaud.net>

arch/arm/lib/bootm.c

@@ -22,6 +22,8 @@
 #include <asm/bootm.h>
 #include <asm/secure.h>
 #include <linux/compiler.h>
+#include <bootm.h>
+#include <vxworks.h>
 
 #if defined(CONFIG_ARMV7_NONSEC) || defined(CONFIG_ARMV7_VIRT)
 #include <asm/armv7.h>
@@ -299,7 +301,8 @@ static void boot_jump_linux(bootm_headers_t *images, int flag)
  * DIFFERENCE: Instead of calling prep and go at the end
  * they are called if subcommand is equal 0.
  */
-int do_bootm_linux(int flag, int argc, char *argv[], bootm_headers_t *images)
+int do_bootm_linux(int flag, int argc, char * const argv[],
+		   bootm_headers_t *images)
 {
 	/* No need for those on ARM */
 	if (flag & BOOTM_STATE_OS_BD_T || flag & BOOTM_STATE_OS_CMDLINE)