hugetlb: remove redundant VM_BUG_ON() in add_reservation_in_range()

When calling hugetlb_resv_map_add(), we've guaranteed that the parameter
'to' is always larger than 'from', so it never returns a negative value
from hugetlb_resv_map_add().  Thus remove the redundant VM_BUG_ON().

Link: https://lkml.kernel.org/r/2b565552f3d06753da1e8dda439c0d96d6d9a5a3.1634797639.git.baolin.wang@linux.alibaba.comSigned-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/hugetlb.c

@@ -445,7 +445,6 @@ static long add_reservation_in_range(struct resv_map *resv, long f, long t,
 		add += hugetlb_resv_map_add(resv, rg, last_accounted_offset,
 					    t, h, h_cg, regions_needed);
 
-	VM_BUG_ON(add < 0);
 	return add;
 }