xen/arm: map_regions_rw_cache: Map the region with p2m->default_access

xen/arm: map_regions_rw_cache: Map the region with p2m->default_access

The parameter 'access' is used by memaccess to restrict temporarily the
permission. This parameter should not be used for other purpose (such
as restricting permanently the permission).

Instead, we should use the default access requested by memacess. When it
is not enabled, the access will be p2m_access_rwx (i.e no restriction
applied).

The type p2m_mmio_direct will map the region read-write and
non-executable before any further restriction by memaccess. Note that
this is already the resulting permission with the curreent combination
of the type and the access. So there is no functional change.

Signed-off-by: Julien Grall <julien.grall@arm.com>
Acked-by: Stefano Stabellini <sstabellini@kernel.org>