Fix sanitization problems running the linker testsuite for the alpha-elf target.

Fix sanitization problems running the linker testsuite for the alpha-elf target.

	PR 26416
	* elf64-alpha.c (elf64_alpha_relax_tls_get_addr): Test for and
	ignore local symbols.
	(elf64_alpha_relax_got_load): Do not check for local dynamic
	symbols.
	(OP_LDA, OP_LDAH, OP_LDQ, OP_BR, OP_BSR): Use unsigned constant
	values.
	(INSN_A) Cast the A parameter to unsigned.
	(INSN_AB): Define in terms of INSN_A.
	(INSN_ABC): Likewise.
	(INSN_ABO): Likewise.
	(INSN_AD): Likewise.