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/tcp.h b/libc/kernel/uapi/linux/tcp.h
index 1ec025f..4cae8d8 100644
--- a/libc/kernel/uapi/linux/tcp.h
+++ b/libc/kernel/uapi/linux/tcp.h
@@ -184,6 +184,8 @@
   __u64 tcpi_bytes_retrans;
   __u32 tcpi_dsack_dups;
   __u32 tcpi_reord_seen;
+  __u32 tcpi_rcv_ooopack;
+  __u32 tcpi_snd_wnd;
 };
 enum {
   TCP_NLA_PAD,