microblaze: Change section flags for noMMU

All files which uses user unified macros from uaccess.h
(get_user/put_user/clear_user/copy_tofrom_user/
strnlen_user and strncpy_user) generate this
warning messages:
Assembler messages:
Warning: ignoring changed section attributes for .discard

Setting up discard executable section flang for __EX_TABLE_SECTION
macro removed all these warnings.
Signed-off-by: Michal Simek <michal.simek@xilinx.com>

arch/microblaze/include/asm/uaccess.h

@@ -108,7 +108,7 @@ static inline int ___range_ok(unsigned long addr, unsigned long size)
 # define __EX_TABLE_SECTION	".section __ex_table,\"a\"\n"
 #else
 # define __FIXUP_SECTION	".section .discard,\"ax\"\n"
-# define __EX_TABLE_SECTION	".section .discard,\"a\"\n"
+# define __EX_TABLE_SECTION	".section .discard,\"ax\"\n"
 #endif
 
 extern unsigned long __copy_tofrom_user(void __user *to,