sched: use maple tree iterator to walk VMAs

sched: use maple tree iterator to walk VMAs

The linked list is slower than walking the VMAs using the maple tree.  We
can't use the VMA iterator here because it doesn't support moving to an
earlier position.

Link: https://lkml.kernel.org/r/20220504011345.662299-33-Liam.Howlett@oracle.com
Link: https://lkml.kernel.org/r/20220621204632.3370049-49-Liam.Howlett@oracle.com
Link: https://lkml.kernel.org/r/20220720021727.17018-49-Liam.Howlett@oracle.com
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: David Howells <dhowells@redhat.com>
Cc: SeongJae Park <sj@kernel.org>
Cc: Will Deacon <will@kernel.org>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: David Hildenbrand <david@redhat.com>
Cc: Hulk Robot <hulkci@huawei.com>
Cc: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>