ksmbd: remove unused is_char_allowed function

clang with W=1 reports
fs/ksmbd/unicode.c:122:19: error: unused function
  'is_char_allowed' [-Werror,-Wunused-function]
static inline int is_char_allowed(char *ch)
                  ^
This function is not used so remove it.
Signed-off-by: Tom Rix <trix@redhat.com>
Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/ksmbd/unicode.c

@@ -113,24 +113,6 @@ cifs_mapchar(char *target, const __u16 src_char, const struct nls_table *cp,
 	goto out;
 }
 
-/*
- * is_char_allowed() - check for valid character
- * @ch:		input character to be checked
- *
- * Return:	1 if char is allowed, otherwise 0
- */
-static inline int is_char_allowed(char *ch)
-{
-	/* check for control chars, wildcards etc. */
-	if (!(*ch & 0x80) &&
-	    (*ch <= 0x1f ||
-	     *ch == '?' || *ch == '"' || *ch == '<' ||
-	     *ch == '>' || *ch == '|'))
-		return 0;
-
-	return 1;
-}
-
 /*
  * smb_from_utf16() - convert utf16le string to local charset
  * @to:		destination buffer