mm: zbud: fix condition check on allocation size

mm: zbud: fix condition check on allocation size

zbud_alloc() incorrectly verifies the size of allocation limit.  It
should deny the allocation request greater than (PAGE_SIZE -
ZHDR_SIZE_ALIGNED - CHUNK_SIZE), not (PAGE_SIZE - ZHDR_SIZE_ALIGNED)
which has no remaining spaces for its buddy.  There is no point in
spending the entire zbud page storing only a single page, since we don't
have any benefits.

Signed-off-by: Heesub Shin <[email protected]>
Acked-by: Seth Jennings <[email protected]>
Cc: Bob Liu <[email protected]>
Cc: Dongjun Shin <[email protected]>
Cc: Sunae Seo <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>