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/media-bus-format.h b/libc/kernel/uapi/linux/media-bus-format.h
index 1b13002..f0d81d0 100644
--- a/libc/kernel/uapi/linux/media-bus-format.h
+++ b/libc/kernel/uapi/linux/media-bus-format.h
@@ -39,6 +39,7 @@
 #define MEDIA_BUS_FMT_RGB888_1X24 0x100a
 #define MEDIA_BUS_FMT_RGB888_2X12_BE 0x100b
 #define MEDIA_BUS_FMT_RGB888_2X12_LE 0x100c
+#define MEDIA_BUS_FMT_RGB888_3X8 0x101c
 #define MEDIA_BUS_FMT_RGB888_1X7X4_SPWG 0x1011
 #define MEDIA_BUS_FMT_RGB888_1X7X4_JEIDA 0x1012
 #define MEDIA_BUS_FMT_ARGB8888_1X32 0x100d