target-ppc: add vcmpnez[b,h,w][.] instructions

target-ppc: add vcmpnez[b,h,w][.] instructions

Adds following instructions:

vcmpnezb[.]: Vector Compare Not Equal or Zero Byte
vcmpnezh[.]: Vector Compare Not Equal or Zero Halfword
vcmpnezw[.]: Vector Compare Not Equal or Zero Word

Signed-off-by: Swapnil Bokade <bokadeswapnil@gmail.com>
[ collapse switch case ]
Signed-off-by: Nikunj A Dadhania <nikunj@linux.vnet.ibm.com>
Reviewed-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>