ARM: Fix another build warning in arch/arm/mm/alignment.c

One such warning was recently fixed in a761cebf "ARM: Fix build warning
in arch/arm/mm/alignment.c" but only for the thumb2 case, this fixes
the other half.

arch/arm/mm/alignment.c: In function 'do_alignment':
arch/arm/mm/alignment.c:327:15: error: 'offset.un' may be used uninitialized in this function
arch/arm/mm/alignment.c:748:21: note: 'offset.un' was declared here
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/mm/alignment.c

@@ -856,8 +856,10 @@ do_alignment(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
 		if (thumb2_32b) {
 			offset.un = 0;
 			handler = do_alignment_t32_to_handler(&instr, regs, &offset);
-		} else
+		} else {
+			offset.un = 0;
 			handler = do_alignment_ldmstm;
+		}
 		break;
 
 	default: