Update to v4.15 kernel headers.

Test: Compiles, boots bullhead/hikey960.
Change-Id: I118beb8b6cac0881b1270f9bf6981959297a41a8
diff --git a/libc/kernel/uapi/linux/dcbnl.h b/libc/kernel/uapi/linux/dcbnl.h
index 569efdd..2fe4cce 100644
--- a/libc/kernel/uapi/linux/dcbnl.h
+++ b/libc/kernel/uapi/linux/dcbnl.h
@@ -91,6 +91,7 @@
 #define IEEE_8021QAZ_APP_SEL_STREAM 2
 #define IEEE_8021QAZ_APP_SEL_DGRAM 3
 #define IEEE_8021QAZ_APP_SEL_ANY 4
+#define IEEE_8021QAZ_APP_SEL_DSCP 5
 struct dcb_app {
   __u8 selector;
   __u8 priority;