target/arm: Add cpu properties for enabling FEAT_RME

target/arm: Add cpu properties for enabling FEAT_RME

Add an x-rme cpu property to enable FEAT_RME.
Add an x-l0gptsz property to set GPCCR_EL3.L0GPTSZ,
for testing various possible configurations.

We're not currently completely sure whether FEAT_RME will
be OK to enable purely as a CPU-level property, or if it will
need board co-operation, so we're making these experimental
x- properties, so that the people developing the system
level software for RME can try to start using this and let
us know how it goes. The command line syntax for enabling
this will change in future, without backwards-compatibility.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20230620124418.805717-21-richard.henderson@linaro.org
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>