MAINTAINERS: add missing headers to mempory policy & migration section

These two files currently do not belong to any section.
The memory policy & migration section seems to be a good home for them!

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Joshua Hahn <[email protected]>
Acked-by: David Hildenbrand <[email protected]>
Cc: Alistair Popple <[email protected]>
Cc: Byungchul Park <[email protected]>
Cc: Gregory Price <[email protected]>
Cc: "Huang, Ying" <[email protected]>
Cc: Lorenzo Stoakes <[email protected]>
Cc: Mathew Brost <[email protected]>
Cc: Rakie Kim <[email protected]>
Cc: Zi Yan <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

Author: joshuahahn

MAINTAINERS

@@ -15849,7 +15849,9 @@ S:	Maintained
 W:	http://www.linux-mm.org
 T:	git git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
 F:	include/linux/mempolicy.h
+F:	include/uapi/linux/mempolicy.h
 F:	include/linux/migrate.h
+F:	include/linux/migrate_mode.h
 F:	mm/mempolicy.c
 F:	mm/migrate.c
 F:	mm/migrate_device.c