ubsan: undefined shift in loongarch_elf_add_sub_reloc_uleb128

An oss-fuzz testcase found:
runtime error: shift exponent 140 is too large for 32-bit type 'int'
OK, that's just a completely silly uleb, but we ought to be able to
handle 64 bits here.

	* elfxx-loongarch.c (loongarch_elf_add_sub_reloc_uleb128): Formatting.
	Don't left shift int.  Avoid shifts larger than bits in a bfd_vma.