hugetlbfs: remove useless BUG_ON(!inode) in hugetlbfs_setattr()

hugetlbfs: remove useless BUG_ON(!inode) in hugetlbfs_setattr()

When we reach here with inode = NULL, we should have crashed as inode has
already been dereferenced via hstate_inode.  So this BUG_ON(!inode) does
not take effect and should be removed.

Link: https://lkml.kernel.org/r/20210118110700.52506-1-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>