sysfs, kernfs: move file core code to fs/kernfs/file.c

Move core file code to fs/kernfs/file.c.  fs/sysfs/file.c now contains
sysfs kernfs_ops callbacks, sysfs wrappers around kernfs interfaces,
and sysfs_schedule_callback().  The respective declarations in
fs/sysfs/sysfs.h are moved to fs/kernfs/kernfs-internal.h.

This is pure relocation.

v2: Refreshed on top of the v2 of "sysfs, kernfs: prepare read path
    for kernfs".

v3: Refreshed on top of the v3 of "sysfs, kernfs: prepare read path
    for kernfs".
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

fs/kernfs/kernfs-internal.h

@@ -142,4 +142,11 @@ int sysfs_add_one(struct sysfs_addrm_cxt *acxt, struct sysfs_dirent *sd,
 void sysfs_addrm_finish(struct sysfs_addrm_cxt *acxt);
 struct sysfs_dirent *sysfs_new_dirent(const char *name, umode_t mode, int type);
 
+/*
+ * file.c
+ */
+extern const struct file_operations kernfs_file_operations;
+
+void sysfs_unmap_bin_file(struct sysfs_dirent *sd);
+
 #endif	/* __KERNFS_INTERNAL_H */

fs/sysfs/sysfs.h

@@ -41,15 +41,11 @@ void sysfs_warn_dup(struct sysfs_dirent *parent, const char *name);
 /*
  * file.c
  */
-extern const struct file_operations kernfs_file_operations;
-
 int sysfs_add_file(struct sysfs_dirent *dir_sd,
 		   const struct attribute *attr, bool is_bin);
-
 int sysfs_add_file_mode_ns(struct sysfs_dirent *dir_sd,
 			   const struct attribute *attr, bool is_bin,
 			   umode_t amode, const void *ns);
-void sysfs_unmap_bin_file(struct sysfs_dirent *sd);
 
 /*
  * symlink.c