target/arm: Convert MSR (reg), MRS, SYS, SYSL to decodetree

Convert MSR (reg), MRS, SYS, SYSL to decodetree.  For QEMU these are
all essentially the same instruction (system register access).

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20230602155223.2040685-7-peter.maydell@linaro.org
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
2 files changed