Fixed syntax error in function init_e300_core() of mpc83xx/start.S if

Signed-off-by: Timur Tabi <timur@freescale.com>
Signed-off-by: Heiko Schocher <hs@denx.de>

cpu/mpc83xx/start.S

diff --git a/cpu/mpc83xx/start.S b/cpu/mpc83xx/start.S
index 496c8a5..1dfbf62 100644
--- a/cpu/mpc83xx/start.S
+++ b/cpu/mpc83xx/start.S
@@ -462,7 +462,7 @@
 
 	li	r4, 0x556C
 	sth	r4, SWSRR@l(r3)
-	li	r4, 0xAA39
+	li	r4, -0x55C7
 	sth	r4, SWSRR@l(r3)
 #else
 	/* Disable Wathcdog  */