arm: sanitizer stringop-overflow

In function 'memset',
    inlined from 'create_unwind_entry' at /home/alan/src/binutils-gdb/gas/config/tc-arm.c:27881:3:
/usr/include/bits/string_fortified.h:59:10: error: '__builtin_memset' specified size between 2147483652 and 4294967295 exceeds maximum object size 2147483647 [-Werror=stringop-overflow=]
   59 |   return __builtin___memset_chk (__dest, __ch, __len,
      |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   60 |                                  __glibc_objsize0 (__dest));
      |                                  ~~~~~~~~~~~~~~~~~~~~~~~~~~

	* config/tc-arm.c (create_unwind_entry): Return after bad size,
	and bad opcode count.