Update to kernel headers v4.12.3.

Test: Built angler.
Change-Id: Icbcf4fac2334de8409b049ed7a3b4c24b4e98ce9
diff --git a/libc/kernel/uapi/linux/input-event-codes.h b/libc/kernel/uapi/linux/input-event-codes.h
index a599b7f..aea69f3 100644
--- a/libc/kernel/uapi/linux/input-event-codes.h
+++ b/libc/kernel/uapi/linux/input-event-codes.h
@@ -564,6 +564,7 @@
 #define KEY_FASTREVERSE 0x275
 #define KEY_SLOWREVERSE 0x276
 #define KEY_DATA 0x277
+#define KEY_ONSCREEN_KEYBOARD 0x278
 #define BTN_TRIGGER_HAPPY 0x2c0
 #define BTN_TRIGGER_HAPPY1 0x2c0
 #define BTN_TRIGGER_HAPPY2 0x2c1