mm/page_alloc: rename alloc_mask to alloc_gfp

mm/page_alloc: rename alloc_mask to alloc_gfp

Patch series "Rationalise __alloc_pages wrappers", v3.

I was poking around the __alloc_pages variants trying to understand why
they each exist, and couldn't really find a good justification for keeping
__alloc_pages and __alloc_pages_nodemask as separate functions.  That led
to getting rid of alloc_pages_current() and then I noticed the
documentation was bad, and then I noticed the mempolicy documentation
wasn't included.

Anyway, this is all cleanups & doc fixes.

This patch (of 7):

We have two masks involved -- the nodemask and the gfp mask, so alloc_mask
is an unclear name.

Link: https://lkml.kernel.org/r/20210225150642.2582252-2-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>