s390/uaccess: add missing earlyclobber annotations to __clear_user()

Add missing earlyclobber annotation to size, to, and tmp2 operands of the
__clear_user() inline assembly since they are modified or written to before
the last usage of all input operands. This can lead to incorrect register
allocation for the inline assembly.

Fixes: 6c2a9e6d ("[S390] Use alternative user-copy operations for new hardware.")
Reported-by: Mark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/all/20230321122514.1743889-3-mark.rutland@arm.com/
Cc: stable@vger.kernel.org
Reviewed-by: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

arch/s390/lib/uaccess.c

@@ -172,7 +172,7 @@ unsigned long __clear_user(void __user *to, unsigned long size)
 		"4: slgr  %0,%0\n"
 		"5:\n"
 		EX_TABLE(0b,2b) EX_TABLE(6b,2b) EX_TABLE(3b,5b) EX_TABLE(7b,5b)
-		: "+a" (size), "+a" (to), "+a" (tmp1), "=a" (tmp2)
+		: "+&a" (size), "+&a" (to), "+a" (tmp1), "=&a" (tmp2)
 		: "a" (empty_zero_page), [spec] "d" (spec.val)
 		: "cc", "memory", "0");
 	return size;