target/arm: Convert MSR (immediate) to decodetree

Convert the MSR (immediate) insn to decodetree. Our implementation
has basically no commonality between the different destinations,
so we decode the destination register in a64.decode.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20230602155223.2040685-6-peter.maydell@linaro.org
2 files changed