MAINTAINERS: add myself as vmalloc co-maintainer

I have been working on the vmalloc code for several years, contributing to
improvements and fixes.  Add myself as co-maintainer ("M") alongside
Andrew Morton.

Link: https://lkml.kernel.org/r/20250507150257.61485-1-urezki@gmail.com
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Acked-by: David Hildenbrand <david@redhat.com>
Acked-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Acked-by: Baoquan He <bhe@redhat.com>
Cc: Christop Hellwig <hch@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

MAINTAINERS

@@ -25906,7 +25906,7 @@ F:	tools/testing/vsock/
 
 VMALLOC
 M:	Andrew Morton <akpm@linux-foundation.org>
-R:	Uladzislau Rezki <urezki@gmail.com>
+M:	Uladzislau Rezki <urezki@gmail.com>
 L:	linux-mm@kvack.org
 S:	Maintained
 W:	http://www.linux-mm.org