target/arm: Use FPST_FPCR_AH for BFMLAL*, BFMLSL* insns

target/arm: Use FPST_FPCR_AH for BFMLAL*, BFMLSL* insns

When FPCR.AH is 1, use FPST_FPCR_AH for:
 * AdvSIMD BFMLALB, BFMLALT
 * SVE BFMLALB, BFMLALT, BFMLSLB, BFMLSLT

so that they get the required behaviour changes.

We do this by making gen_gvec_op4_fpst() take an ARMFPStatusFlavour
rather than a bool is_fp16; existing callsites now select
FPST_FPCR_F16_A64 vs FPST_FPCR_A64 themselves rather than passing in
the boolean.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>