microblaze: Fix _reset function

If soft reset falls through with no hardware assisted reset, the best
we can do is jump to the reset vector and see what the bootloader left
for us.
Signed-off-by: Michal Simek <monstr@monstr.eu>
Signed-off-by: John Williams <john.williams@petalogix.com>

arch/microblaze/kernel/entry.S

@@ -988,7 +988,7 @@ ENTRY(_switch_to)
 	nop
 
 ENTRY(_reset)
-	brai	0x70; /* Jump back to FS-boot */
+	brai	0; /* Jump to reset vector */
 
 	/* These are compiled and loaded into high memory, then
 	 * copied into place in mach_early_setup */