hugetlb: fix error return for brk() entering a hugepage region

The lats commit causes the wrong return value.
is_hugepage_only_range() is a boolean, so we should return
-EINVAL rather than 1.

Also - we can use "mm" instead of looking up "current->mm" again.
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Adrian Bunk <bunk@kernel.org>

mm/mmap.c

@@ -1870,9 +1870,8 @@ unsigned long do_brk(unsigned long addr, unsigned long len)
 	if ((addr + len) > TASK_SIZE || (addr + len) < addr)
 		return -EINVAL;
 
-	error = is_hugepage_only_range(current->mm, addr, len);
-	if (error)
-		return error;
+	if (is_hugepage_only_range(mm, addr, len))
+		return -EINVAL;
 
 	flags = VM_DATA_DEFAULT_FLAGS | VM_ACCOUNT | mm->def_flags;