target/ppc: Implemented xvi*ger* instructions

Implement the following PowerISA v3.1 instructions:
xvi4ger8:     VSX Vector 8-bit Signed/Unsigned Integer GER (rank-4 update)
xvi4ger8pp:   VSX Vector 8-bit Signed/Unsigned Integer GER (rank-4 update)
Positive multiply, Positive accumulate
xvi8ger4:     VSX Vector 4-bit Signed Integer GER (rank-8 update)
xvi8ger4pp:   VSX Vector 4-bit Signed Integer GER (rank-8 update)
Positive multiply, Positive accumulate
xvi8ger4spp:  VSX Vector 8-bit Signed/Unsigned Integer GER (rank-4 update)
with Saturate Positive multiply, Positive accumulate
xvi16ger2:    VSX Vector 16-bit Signed Integer GER (rank-2 update)
xvi16ger2pp:  VSX Vector 16-bit Signed Integer GER (rank-2 update)
Positive multiply, Positive accumulate
xvi16ger2s:   VSX Vector 16-bit Signed Integer GER (rank-2 update)
with Saturation
xvi16ger2spp: VSX Vector 16-bit Signed Integer GER (rank-2 update)
with Saturation Positive multiply, Positive accumulate

Signed-off-by: Lucas Mateus Castro (alqotel) <lucas.araujo@eldorado.org.br>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20220524140537.27451-3-lucas.araujo@eldorado.org.br>
Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>