target/arm: Update translation regime comment for new features

target/arm: Update translation regime comment for new features

We have a long comment describing the Arm architectural translation
regimes and how we map them to QEMU MMU indexes.  This comment has
got a bit out of date:

 * FEAT_SEL2 allows Secure EL2 and corresponding new regimes
 * FEAT_RME introduces Realm state and its translation regimes
 * We now model the Cortex-R52 so that is no longer a hypothetical
 * We separated Secure Stage 2 and NonSecure Stage 2 MMU indexes
 * We have an MMU index per physical address spacea

Add the missing pieces so that the list of architectural translation
regimes matches the Arm ARM, and the list and count of QEMU MMU
indexes in the comment matches the enum.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Tested-by: Bernhard Beschow <shentey@gmail.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20240809160430.1144805-2-peter.maydell@linaro.org