btrfs: rename struct-funcs.c to accessors.c

btrfs-y += super.o ctree.o extent-tree.o print-tree.o root-tree.o dir-item.o \

	   file-item.o inode-item.o disk-io.o \

	   transaction.o inode.o file.o tree-defrag.o \

	   extent_map.o sysfs.o struct-funcs.o xattr.o ordered-data.o \

	   extent_map.o sysfs.o accessors.o xattr.o ordered-data.o \

	   extent_io.o volumes.o async-thread.o ioctl.o locking.o orphan.o \

	   export.o tree-log.o free-space-cache.o zlib.o lzo.o zstd.o \

	   compression.o delayed-ref.o relocation.o delayed-inode.o scrub.o \

 */

#include <asm/unaligned.h>

#include "messages.h"

#include "ctree.h"