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_sched.h b/libc/kernel/uapi/linux/pkt_sched.h
index 15ee3b0..c287e8c 100644
--- a/libc/kernel/uapi/linux/pkt_sched.h
+++ b/libc/kernel/uapi/linux/pkt_sched.h
@@ -877,7 +877,8 @@
   __TCA_TAPRIO_SCHED_MAX,
 };
 #define TCA_TAPRIO_SCHED_MAX (__TCA_TAPRIO_SCHED_MAX - 1)
-#define TCA_TAPRIO_ATTR_FLAG_TXTIME_ASSIST 0x1
+#define TCA_TAPRIO_ATTR_FLAG_TXTIME_ASSIST BIT(0)
+#define TCA_TAPRIO_ATTR_FLAG_FULL_OFFLOAD BIT(1)
 enum {
   TCA_TAPRIO_ATTR_UNSPEC,
   TCA_TAPRIO_ATTR_PRIOMAP,