refactor(cm): unify RMM context

setup_realm_context() is the de facto place to put any code that relates
to the RMM's context. It is frequently updated and contains the vast
majority of code. manage_extensions_realm() on the other hand is out of
date and obscure.

So absorb manage_extensions_realm() and rmm_el2_context_init() into
setup_realm_context().

We can also combine the write to sctlr_el2 for all worlds as they should
all observe the RES1 values.

Finally, the SPSR_EL2.PAN comment in the realm copy is updated.

Change-Id: I21dccad0c13301e3249db6f6e292beb5d853563e
Signed-off-by: Boyan Karatotev <boyan.karatotev@arm.com>
4 files changed