ubifs: fix checkpatch warning

Fix the following checkpatch warning:-

WARNING: externs should be avoided in .c files

Signed-off-by: Murali Karicheri <m-karicheri2@ti.com>

common/cmd_ubifs.c

@@ -21,15 +21,6 @@
 static int ubifs_initialized;
 static int ubifs_mounted;
 
-extern struct super_block *ubifs_sb;
-
-/* Prototypes */
-int ubifs_init(void);
-int ubifs_mount(char *vol_name);
-void ubifs_umount(struct ubifs_info *c);
-int ubifs_ls(char *dir_name);
-int ubifs_load(char *filename, u32 addr, u32 size);
-
 int do_ubifs_mount(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
 {
 	char *vol_name;

fs/ubifs/ubifs.h

@@ -2137,6 +2137,13 @@ void ubifs_compress(const void *in_buf, int in_len, void *out_buf, int *out_len,
 int ubifs_decompress(const void *buf, int len, void *out, int *out_len,
 		     int compr_type);
 
+/* these are used in cmd_ubifs.c */
+int ubifs_init(void);
+int ubifs_mount(char *vol_name);
+void ubifs_umount(struct ubifs_info *c);
+int ubifs_ls(char *dir_name);
+int ubifs_load(char *filename, u32 addr, u32 size);
+
 #include "debug.h"
 #include "misc.h"
 #include "key.h"