system_dlkm: sepolicy: add system_dlkm_file_type

Add new attribute system_dlkm_file_type for
/system_dlkm partition files.

Bug: 218392646
Bug: 200082547
Test: TH
Signed-off-by: Ramji Jiyani <ramjiyani@google.com>
Change-Id: I193c3f1270f7a1b1259bc241def3fe51d77396f3
diff --git a/private/file_contexts b/private/file_contexts
index ba50376..da9215f 100644
--- a/private/file_contexts
+++ b/private/file_contexts
@@ -19,7 +19,7 @@
 
 # For kernel modules
 /lib(/.*)?          u:object_r:rootfs:s0
-/system_dlkm(/.*)?  u:object_r:rootfs:s0
+/system_dlkm(/.*)?  u:object_r:system_dlkm_file:s0
 
 # Empty directories
 /lost\+found        u:object_r:rootfs:s0