[MIPS] Initialize CP0 Cause before setting up CP0 Status register

Without this change, we'll be suffering from deffered WATCH exception
once Status.EXL is cleared. Make sure Cause.WP is cleared.
Signed-off-by: NShinya Kuribayashi <skuribay@ruby.dti.ne.jp>

cpu/mips/start.S

@@ -211,6 +211,9 @@ reset:
 	mtc0	zero, CP0_WATCHLO
 	mtc0	zero, CP0_WATCHHI
 
+	/* WP(Watch Pending), SW0/1 should be cleared. */
+	mtc0	zero, CP0_CAUSE
+
 	/* STATUS register */
 #ifdef  CONFIG_TB0229
 	li	k0, ST0_CU0
@@ -221,9 +224,6 @@ reset:
 	and	k0, k1
 	mtc0	k0, CP0_STATUS
 
-	/* CAUSE register */
-	mtc0	zero, CP0_CAUSE
-
 	/* Init Timer */
 	mtc0	zero, CP0_COUNT
 	mtc0	zero, CP0_COMPARE