target/arm: Move FPU/SVE/SME access checks up above ARM_CP_SPECIAL_MASK check

target/arm: Move FPU/SVE/SME access checks up above ARM_CP_SPECIAL_MASK check

In handle_sys() we don't do the check for whether the register is
marked as needing an FPU/SVE/SME access check until after we've
handled the special cases covered by ARM_CP_SPECIAL_MASK.  This is
conceptually the wrong way around, because if for example we happen
to implement an FPU-access-checked register as ARM_CP_NOP, we should
do the access check first.

Move the access checks up so they are with all the other access
checks, not sandwiched between the special-case read/write handling
and the normal-case read/write handling. This doesn't change
behaviour at the moment, because we happen not to define any
cpregs with both ARM_CPU_{FPU,SVE,SME} and one of the cases
dealt with by ARM_CP_SPECIAL_MASK.

Moving this code also means we have the correct place to put the
FEAT_NV/FEAT_NV2 access handling, which should come after the access
checks and before we try to do any read/write action.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Tested-by: Miguel Luis <miguel.luis@oracle.com>