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/openvswitch.h b/libc/kernel/uapi/linux/openvswitch.h
index 2344ab1..581a371 100644
--- a/libc/kernel/uapi/linux/openvswitch.h
+++ b/libc/kernel/uapi/linux/openvswitch.h
@@ -70,6 +70,7 @@
 };
 #define OVS_DP_F_UNALIGNED (1 << 0)
 #define OVS_DP_F_VPORT_PIDS (1 << 1)
+#define OVS_DP_F_TC_RECIRC_SHARING (1 << 2)
 #define OVSP_LOCAL ((__u32) 0)
 #define OVS_PACKET_FAMILY "ovs_packet"
 #define OVS_PACKET_VERSION 0x1