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/btrfs_tree.h b/libc/kernel/uapi/linux/btrfs_tree.h
index be0c8b0..5f58100 100644
--- a/libc/kernel/uapi/linux/btrfs_tree.h
+++ b/libc/kernel/uapi/linux/btrfs_tree.h
@@ -92,7 +92,9 @@
 #define BTRFS_UUID_KEY_RECEIVED_SUBVOL 252
 #define BTRFS_STRING_ITEM_KEY 253
 #define BTRFS_CSUM_SIZE 32
-#define BTRFS_CSUM_TYPE_CRC32 0
+enum btrfs_csum_type {
+  BTRFS_CSUM_TYPE_CRC32 = 0,
+};
 #define BTRFS_FT_UNKNOWN 0
 #define BTRFS_FT_REG_FILE 1
 #define BTRFS_FT_DIR 2
@@ -344,11 +346,6 @@
 } __attribute__((__packed__));
 #define BTRFS_DEV_REPLACE_ITEM_CONT_READING_FROM_SRCDEV_MODE_ALWAYS 0
 #define BTRFS_DEV_REPLACE_ITEM_CONT_READING_FROM_SRCDEV_MODE_AVOID 1
-#define BTRFS_DEV_REPLACE_ITEM_STATE_NEVER_STARTED 0
-#define BTRFS_DEV_REPLACE_ITEM_STATE_STARTED 1
-#define BTRFS_DEV_REPLACE_ITEM_STATE_SUSPENDED 2
-#define BTRFS_DEV_REPLACE_ITEM_STATE_FINISHED 3
-#define BTRFS_DEV_REPLACE_ITEM_STATE_CANCELED 4
 struct btrfs_dev_replace_item {
   __le64 src_devid;
   __le64 cursor_left;