[ARM] Allow MOV/MOV.W to accept all possible immediates

[ARM] Allow MOV/MOV.W to accept all possible immediates

gas/
	* config/tc-arm.c (SBIT_SHIFT): New.
	(T2_SBIT_SHIFT): Likewise.
	(t32_insn_ok): Return TRUE for MOV in ARMv8-M Baseline.
	(md_apply_fix): Try UINT16 encoding when ARM/Thumb modified immediate
	encoding failed.
	* testsuite/gas/arm/archv6t2-bad.s: New error case.
	* testsuite/gas/arm/archv6t2-bad.l: New error match.
	* testsuite/gas/arm/archv6t2.s: New testcase.
	* testsuite/gas/arm/archv6t2.d: New expected result.
	* testsuite/gas/arm/archv8m.s: New testcase.
	* testsuite/gas/arm/archv8m-base.d: New expected result.
	* testsuite/gas/arm/archv8m-main.d: Likewise.
	* testsuite/gas/arm/archv8m-main-dsp-1.d: Likewise.