target/ppc: implement lxvr[bhwd]/stxvr[bhwd]x

target/ppc: implement lxvr[bhwd]/stxvr[bhwd]x

Implement the following PowerISA v3.1 instuctions:
lxvrbx: Load VSX Vector Rightmost Byte Indexed X-form
lxvrhx: Load VSX Vector Rightmost Halfword Indexed X-form
lxvrwx: Load VSX Vector Rightmost Word Indexed X-form
lxvrdx: Load VSX Vector Rightmost Doubleword Indexed X-form

stxvrbx: Store VSX Vector Rightmost Byte Indexed X-form
stxvrhx: Store VSX Vector Rightmost Halfword Indexed X-form
stxvrwx: Store VSX Vector Rightmost Word Indexed X-form
stxvrdx: Store VSX Vector Rightmost Doubleword Indexed X-form

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Lucas Coutinho <lucas.coutinho@eldorado.org.br>
Signed-off-by: Matheus Ferst <matheus.ferst@eldorado.org.br>
Message-Id: <20220225210936.1749575-50-matheus.ferst@eldorado.org.br>
Signed-off-by: Cédric Le Goater <clg@kaod.org>