gas/config/tc-arm.c: Improve validation of NEON addressing modes.

gas/config/tc-arm.c: Improve validation of NEON addressing modes.

NEON vector load and store instructions do not accept immediates
or pre-indexed base plus offset addressing modes, so make sure that
the assembler enforces this.

gas/ChangeLog:

2013-08-23  Will Newton  <will.newton@linaro.org>

	* config/tc-arm.c (do_neon_ldx_stx): Add extra constraints
	for pre-indexed addressing modes.
	* testsuite/gas/arm/neon-addressing-bad.l: Add test for
	VLDn and VSTn instructions.
	* testsuite/gas/arm/neon-addressing-bad.s: Likewise.

gas/testsuite/ChangeLog:

2013-08-23  Will Newton  <will.newton@linaro.org>

	* testsuite/gas/arm/neon-addressing-bad.l: Add test for
	VLDn and VSTn instructions.
	* testsuite/gas/arm/neon-addressing-bad.s: Likewise.