Security: remove security_file_mmap hook sparse-warnings (NULL as 0).

Fixing:
  CHECK   mm/mmap.c
mm/mmap.c:1623:29: warning: Using plain integer as NULL pointer
mm/mmap.c:1623:29: warning: Using plain integer as NULL pointer
mm/mmap.c:1944:29: warning: Using plain integer as NULL pointer

Signed-off-by: Richard Knutsson <ricknu-0@student.ltu.se>
Signed-off-by: James Morris <jmorris@namei.org>

mm/mmap.c

diff --git a/mm/mmap.c b/mm/mmap.c
index 15678aa..bfa389f 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1620,7 +1620,7 @@
 		return -ENOMEM;
 
 	address &= PAGE_MASK;
-	error = security_file_mmap(0, 0, 0, 0, address, 1);
+	error = security_file_mmap(NULL, 0, 0, 0, address, 1);
 	if (error)
 		return error;
 
@@ -1941,7 +1941,7 @@
 	if (is_hugepage_only_range(mm, addr, len))
 		return -EINVAL;
 
-	error = security_file_mmap(0, 0, 0, 0, addr, 1);
+	error = security_file_mmap(NULL, 0, 0, 0, addr, 1);
 	if (error)
 		return error;