target/arm: Allow FPCR bits that aren't in FPSCR

target/arm: Allow FPCR bits that aren't in FPSCR

In order to allow FPCR bits that aren't in the FPSCR (like the new
bits that are defined for FEAT_AFP), we need to make sure that writes
to the FPSCR only write to the bits of FPCR that are architecturally
mapped, and not the others.

Implement this with a new function vfp_set_fpcr_masked() which
takes a mask of which bits to update.

(We could do the same for FPSR, but we leave that until we actually
are likely to need it.)

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20240628142347.1283015-10-peter.maydell@linaro.org