Move the unlock earlier in user_mem_abort() to shorten the
critical section. This also helps for future refactoring and
reuse of similar code.

This moves out marking the page as dirty outside of the critical
section. That code does not interact with the stage-2 page
tables, which the read lock in the critical section protects.
Signed-off-by: Fuad Tabba <tabba@google.com>
Acked-by: Oliver Upton <oliver.upton@linux.dev>
Link: https://lore.kernel.org/r/20240423150538.2103045-16-tabba@google.comSigned-off-by: Marc Zyngier <maz@kernel.org>