Documentation/features/vm: Meta2 is capable of THP

Change metag Transparent Huge Pages (THP) support from .. to TODO. Meta2
has variable sized pages, between 4KB and 4MB, specified at the 1st
level page table level, and already supports hugetlbfs, so supporting
THP is theoretically possible too.

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: linux-metag@vger.kernel.org
Cc: linux-doc@vger.kernel.org