mm/page_alloc: use might_alloc()

mm/page_alloc: use might_alloc()

...  instead of open coding it.  Completely equivalent code, just a notch
more meaningful when reading.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Daniel Vetter <[email protected]>
Reviewed-by: David Hildenbrand <[email protected]>
Reviewed-by: Vlastimil Babka <[email protected]>
Cc: Christoph Lameter <[email protected]>
Cc: David Rientjes <[email protected]>
Cc: Joonsoo Kim <[email protected]>
Cc: Pekka Enberg <[email protected]>
Cc: Roman Gushchin <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>