mm/hugetlb: remove redundant check in preparing and destroying gigantic page

Gigantic page is a compound page and its order is more than 1.  Thus it
must be available for hpage_pincount.  Let's remove the redundant check
for gigantic page.

Link: https://lkml.kernel.org/r/20210202112002.73170-1-yanfei.xu@windriver.com


Signed-off-by: Yanfei Xu <yanfei.xu@windriver.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>