mmzone: introduce folio_migratetype()

Introduce folio_migratetype() as a folio equivalent for
get_pageblock_migratetype().  This function intends to return the
migratetype the folio is located in, hence the name choice.

Link: https://lkml.kernel.org/r/20230614021312.34085-3-vishal.moola@gmail.com


Signed-off-by: Vishal Moola (Oracle) <vishal.moola@gmail.com>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>