Blackfin arch: fix bug - Turn on DEBUG_DOUBLEFAULT, booting SMP kernel crash

Signed-off-by: Graf Yang <graf.yang@analog.com>
Signed-off-by: Bryan Wu <cooloney@kernel.org>

arch/blackfin/mach-common/entry.S

@@ -277,7 +277,7 @@ ENTRY(_bfin_return_from_exception)
 	p5.h = hi(ILAT);
 	r6 = [p5];
 	r7 = 0x20;		/* Did I just cause anther HW error? */
-	r7 = r7 & r1;
+	r6 = r7 & r6;
 	CC = R7 == R6;
 	if CC JUMP _double_fault;
 #endif