LoongArch: binutils: Add support for linker relaxation.

Add support for relocs related to relax to readelf.

binutils/ChangeLog:

	* readelf.c (target_specific_reloc_handling): Handle ULEB128 reloc.
	(is_32bit_inplace_add_reloc): Handle new reloc.
	(is_32bit_inplace_sub_reloc): Likewise.
	(is_64bit_inplace_add_reloc): Likewise.
	(is_64bit_inplace_sub_reloc): Likewise.
	(is_16bit_inplace_add_reloc): Likewise.
	(is_16bit_inplace_sub_reloc): Likewise.
	(is_8bit_inplace_add_reloc): Likewise.
	(is_8bit_inplace_sub_reloc): Likewise.
	(is_6bit_inplace_sub_reloc): Likewise.
	(is_6bit_inplace_add_reloc): New function.
	(apply_relocations): Handle new reloc.
	* testsuite/binutils-all/readelf.exp: Add -mno-relax option
	for LoongArch.