MAINTAINERS: add memory mapping/VMA co-maintainers

Add myself and Liam as co-maintainers of the memory mapping and VMA code
alongside Andrew as we are heavily involved in its implementation and
maintenance.

Link: https://lkml.kernel.org/r/20241009201032.6130-1-lorenzo.stoakes@oracle.com


Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>