Implement the "Load VSX Vector Word & Splat Indexed" opcode, introduced
in Power ISA v3.0.

Buglink: https://bugs.launchpad.net/qemu/+bug/1793608


Signed-off-by: Giuseppe Musacchio <thatlemon@gmail.com>
Message-Id: <d7d533e18c2bc10d924ee3e09907ff2b41fddb3a.1604912739.git.thatlemon@gmail.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>