migrate: convert unmap_and_move_huge_page() to use folios

Saves several calls to compound_head() and removes a couple of uses of
page->lru.

Link: https://lkml.kernel.org/r/20220902194653.1739778-52-willy@infradead.org


Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>