target/ppc: Moving VSX scalar storage access insns to decodetree.

target/ppc: Moving VSX scalar storage access insns to decodetree.

Moving the following instructions to decodetree specification :

	lxs{d, iwa, ibz, ihz, iwz, sp}x		: X-form
	stxs{d, ib, ih, iw, sp}x		: X-form

The changes were verified by validating that the tcg-ops generated by those
instructions remain the same, which were captured using the '-d in_asm,op' flag.

Signed-off-by: Chinmay Rath <rathc@linux.ibm.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>