Update to android-mainline kernel headers v5.4.

Update generate_uapi_headers.sh to checkout the android mainline
kernel. Also, add a small modification to look for the kernel directory
in common not linux-stable.

Remove deprecated android headers from android/uapi/linux. Also,
remove f_accessory.h since it's in the android mainline kernel.

Test: Builds and runs on walleye.
Change-Id: Ia371305e19f56e6bcc2db6d5b4d299819f07ffc6
diff --git a/libc/kernel/uapi/linux/pkt_cls.h b/libc/kernel/uapi/linux/pkt_cls.h
index 0727916..cc5518c 100644
--- a/libc/kernel/uapi/linux/pkt_cls.h
+++ b/libc/kernel/uapi/linux/pkt_cls.h
@@ -137,6 +137,8 @@
   TCA_POLICE_RESULT,
   TCA_POLICE_TM,
   TCA_POLICE_PAD,
+  TCA_POLICE_RATE64,
+  TCA_POLICE_PEAKRATE64,
   __TCA_POLICE_MAX
 #define TCA_POLICE_RESULT TCA_POLICE_RESULT
 };