ld/x86-64: Properly Handle -z lam-u48/lam-u57

Properly merge GNU properties for LAM_U48 and LAM_U57.

bfd/

	PR ld/27166
	* elfxx-x86.c (_bfd_x86_elf_merge_gnu_properties): Handle
	-z lam-u48 and -z lam-u57.

ld/

	PR ld/27166
	* testsuite/ld-x86-64/lam-u48.rd: New file.
	* testsuite/ld-x86-64/lam-u57.rd: Likewise.
	* testsuite/ld-x86-64/x86-64.exp: Add PR ld/27166 tests.