target-arm: Remove ARMCPU/CPUARMState from cpregs APIs used by decoder

target-arm: Remove ARMCPU/CPUARMState from cpregs APIs used by decoder

The cpregs APIs used by the decoder (get_arm_cp_reginfo() and
cp_access_ok()) currently take either a CPUARMState* or an ARMCPU*.
This is problematic for the A64 decoder, which doesn't pass the
environment pointer around everywhere the way the 32 bit decoder
does. Adjust the parameters these functions take so that we can
copy only the relevant info from the CPUARMState into the
DisasContext and then use that.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <rth@twiddle.net>