Alloc memory for mutex.
Remove unused function to reduce dependencies.
Remove xfs_bmap_btree_to_extents to release xfs_trans_binval.
Resolve spin_lock.
Remove spinlock from left_functions.

spinlock are also called from xfs_inode.h and xfs_trans_priv.h.
But those functions are not needed for us.
Remove rcu lock. Might be updated later.
rcu locks are only read in xfsd_mount.c
Remove mutex_init as well.