target/arm: Implement M-profile VPR register

If MVE is implemented for an M-profile CPU then it has a VPR
register, which tracks predication information.

Implement the read and write handling of this register, and
the migration of its state.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20210520152840.24453-7-peter.maydell@linaro.org
3 files changed