s390: do not clobber personality flags in sys_32_personality()

There are multiple errors in how sys_32_personality() handles personality
flags stored in top three bytes.

- directly comparing current->personality against PER_LINUX32 doesn't work
in cases when any of the personality flags stored in the top three bytes
are used.
- directly forcefully setting personality to PER_LINUX32 or PER_LINUX
discards any flags stored in the top three bytes

Fix the first one by properly using personality() macro to compare only
PER_MASK bytes.
Fix the second one by setting only the bits that should be set, instead of
overwriting the whole value.

Signed-off-by: Jiri Kosina <[e-mail]>
Signed-off-by: Heiko Carstens <[e-mail]>
Signed-off-by: Martin Schwidefsky <[e-mail]>

arch/s390/kernel/sys_s390.c

···
 {
 	unsigned int ret;
 
-	if (current->personality == PER_LINUX32 && personality == PER_LINUX)
-		personality = PER_LINUX32;
+	if (personality(current->personality) == PER_LINUX32 &&
+	    personality(personality) == PER_LINUX)
+		personality |= PER_LINUX32;
 	ret = sys_personality(personality);
-	if (ret == PER_LINUX32)
-		ret = PER_LINUX;
+	if (personality(ret) == PER_LINUX32)
+		ret &= ~PER_LINUX32;
 
 	return ret;
 }