target/ppc: Move VMX integer max/min instructions to decodetree.

target/ppc: Move VMX integer max/min instructions to decodetree.

Moving the following instructions to decodetree specification :

	v{max, min}{u, s}{b, h, w, d}	: VX-form

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

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