btrfs: use may_create_dentry() in btrfs_mksubvol()

btrfs: use may_create_dentry() in btrfs_mksubvol()

There is no longer the need to use btrfs_may_create(), which was a copy
of the VFS private function may_create(), since now that functionality
is exported by the VFS as a function named may_create_dentry(). So change
btrfs_mksubvol() to use the VFS function and remove btrfs_may_create().

Note that the btrfs copy was missing an audit_inode_child() call that we
have in the VFS function. This only reinforces the need to use a common
function, as it's very easy for the btrfs copy to get out of sync and
therefore a maintenance burden.

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Link: https://patch.msgid.link/adf8c802c77ec1c855ea9fe12491120ccc29a294.1768307858.git.fdmanana@suse.com
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>