MAINTAINERS: include linux-mm for xarray maintenance

MM developers have an interest in the xarray code.

Cc: David Gow <[email protected]>
Cc: Geert Uytterhoeven <[email protected]>
Cc: "Liam R. Howlett" <[email protected]>
Cc: Lorenzo Stoakes <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Sidhartha Kumar <[email protected]>
Cc: Tamir Duberstein <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

Author: akpm00

MAINTAINERS

@@ -25729,6 +25729,7 @@ F:	arch/x86/entry/vdso/
 XARRAY
 M:	Matthew Wilcox <[email protected]>
 L:	[email protected]
+L:	[email protected]
 S:	Supported
 F:	Documentation/core-api/xarray.rst
 F:	include/linux/idr.h