mm: add merging after mremap resize

mm: add merging after mremap resize

When mremap call results in expansion, it might be possible to merge the
VMA with the next VMA which might become adjacent.  This patch adds
vma_merge call after the expansion is done to try and merge.

[[email protected]: coding-style cleanups]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Jakub Matěna <[email protected]>
Reviewed-by: Vlastimil Babka <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: "Kirill A . Shutemov" <[email protected]>
Cc: Liam Howlett <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Peter Zijlstra (Intel) <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Steven Rostedt <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>