Avoid excess icache flushes in populate_physmap() before domain has been created

Avoid excess icache flushes in populate_physmap() before domain has been created

populate_physmap() calls alloc_heap_pages() per requested
extent. alloc_heap_pages() invalidates the entire icache per
extent. During domain creation, the icache invalidations can be deffered
until all the extents have been allocated as there is no risk of
executing stale instructions from the icache.

Introduce a new flag "MEMF_no_icache_flush" to be used to prevent
alloc_heap_pages() from performing icache maintenance operations. Use
the flag in populate_physmap() before the domain has been unpaused and
perform required icache maintenance function at the end of the
allocation.

One concern is the lack of synchronisation around testing for
"creation_finished". But it seems, in practice the window where it is
out of sync should be small enough to not matter.

Signed-off-by: Punit Agrawal <punit.agrawal@arm.com>
Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>