omap4: Check warm reset for reboot mode validity

Since the SAR registers are filled with garbage on cold reset, this checks for a
warm reset to assert the validity of reboot mode.
Signed-off-by: NPaul Kocialkowski <contact@paulk.fr>

arch/arm/cpu/armv7/omap4/boot.c

@@ -9,6 +9,7 @@
 #include <common.h>
 #include <asm/io.h>
 #include <asm/omap_common.h>
+#include <asm/arch/sys_proto.h>
 #include <spl.h>
 
 static u32 boot_devices[] = {
@@ -67,6 +68,9 @@ int omap_reboot_mode(char *mode, unsigned int length)
 	if (length < 2)
 		return -1;
 
+	if (!warm_reset())
+		return -1;
+
 	limit = (length < OMAP_REBOOT_REASON_SIZE) ? length :
 		OMAP_REBOOT_REASON_SIZE;