PR26420, PR26421, PR26425, PR26427 UBSAN: tc-arm.c left shifts

	PR 26420
	PR 26421
	PR 26425
	PR 26427
	* config/tc-arm.c (struct arm_it): Make size, size_req, cond and
	uncond_value unsigned.
	(parse_vfp_reg_list): Make setmask unsigned, vpr_str_len size_t.
	(parse_big_immediate): Cast generic_bignum elements to unsigned.
	(encode_thumb32_immediate): Shift left 0xffU.
	(double_to_single): Make sign unsigned.  Tidy.
	(move_or_literal_pool): Cast LITTLE_NUM elements to uint64_t or
	valueT.
	(vfp_or_neon_is_neon): Adjust inst.uncond_value expression.
	(md_assemble): Likewise.
	(handle_pred_state): Make cond unsigned.
	(thumb32_negate_data_op): Make variables unsigned.
	(md_apply_fix): Make value and newval unsigned, adjust uses.