Update to v5.11 kernel headers.

Kernel headers coming from:

Git: https://android.googlesource.com/kernel/common/
Branch: android-mainline
Tag: android-mainline-5.11

Test: Built cuttlefish and flame images. Ran bionic unit tests on both.
Change-Id: Ie60337aafad4bda55af99b6c8fe9f56bf2fa787f
diff --git a/libc/kernel/uapi/linux/btrfs_tree.h b/libc/kernel/uapi/linux/btrfs_tree.h
index 2a9178d..4e36c37 100644
--- a/libc/kernel/uapi/linux/btrfs_tree.h
+++ b/libc/kernel/uapi/linux/btrfs_tree.h
@@ -92,6 +92,7 @@
 #define BTRFS_UUID_KEY_SUBVOL 251
 #define BTRFS_UUID_KEY_RECEIVED_SUBVOL 252
 #define BTRFS_STRING_ITEM_KEY 253
+#define BTRFS_MAX_METADATA_BLOCKSIZE 65536
 #define BTRFS_CSUM_SIZE 32
 enum btrfs_csum_type {
   BTRFS_CSUM_TYPE_CRC32 = 0,