target/arm: Fix PSEL size operands to tcg_gen_gvec_ands

target/arm: Fix PSEL size operands to tcg_gen_gvec_ands

Gvec only operates on size 8 and multiples of 16.
Predicates may be any multiple of 2.
Round up the size using the appropriate function.

Cc: qemu-stable@nongnu.org
Fixes: 598ab0b24c0 ("target/arm: Implement PSEL")
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20250704142112.1018902-8-richard.henderson@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>