xlat v2: Support the EL2 translation regime

xlat v2: Support the EL2 translation regime

The translation library is useful elsewhere. Even though this repository
doesn't exercise the EL2 support of the library, it is better to have it
here as well to make it easier to maintain.

enable_mmu_secure() and enable_mmu_direct() have been deprecated. The
functions are still present, but they are behind ERROR_DEPRECATED and
they call the new functions enable_mmu_svc_mon() and
enable_mmu_direct_svc_mon().

Change-Id: I13ad10cd048d9cc2d55e0fff9a5133671b67dcba
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>