target/arm: mark the 32bit alias of PAR when LPAE enabled

We also mark it ARM_CP_NO_GDB so we avoid duplicate PAR's in the
system register XML we send to gdb.

Suggested-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20231107105145.2916124-1-alex.bennee@linaro.org>