s390/32: Don't clobber personality flags on exec

In native 32 bit mode the personality flags were not correctly inherited.
This is the s390 version of 59e4c3a2 "powerpc/32: Don't clobber personality
flags on exec".
Reported-by: NMike Frysinger <vapier@gentoo.org>
Signed-off-by: NHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/include/asm/elf.h

@@ -180,7 +180,8 @@ extern char elf_platform[];
 #define ELF_PLATFORM (elf_platform)
 
 #ifndef CONFIG_64BIT
-#define SET_PERSONALITY(ex) set_personality(PER_LINUX)
+#define SET_PERSONALITY(ex) \
+	set_personality(PER_LINUX | (current->personality & (~PER_MASK)))
 #else /* CONFIG_64BIT */
 #define SET_PERSONALITY(ex)					\
 do {								\