Fix feature checks based on ARM architecture value

Fix feature checks based on ARM architecture value

2016-06-14  Thomas Preud'homme  <thomas.preudhomme@arm.com>

bfd/
	* elf32-arm.c (using_thumb_only): Force review of arch check logic for
	new architecture.
	(using_thumb2): Try Tag_THUMB_ISA_use first and check
	for exact arch value then.  Force review of arch check logic for new
	architecture.
	(arch_has_arm_nop): Update and fix arch check logic.  Force review of
	that logic for new architecture.
	(arch_has_thumb2_nop): Remove.
	(elf32_arm_tls_relax): Use using_thumb2 instead of above function.
	(elf32_arm_final_link_relocate): Likewise but using thumb2.