Fix sign comparison compiler warnings

src/docsis.c

@@ -456,7 +456,7 @@ setup_mib_flags() {
 
 char *get_output_name ( char *input_path, char *extension_string )
 {
-  int pathlen=0, i=0, old_ext_len=0;
+  size_t pathlen=0, i=0, old_ext_len=0;
   char *new_path;
 
   if (input_path == NULL || extension_string == NULL)

src/docsis_decode.c

@@ -116,7 +116,7 @@ void decode_ethermask (unsigned char *tlvbuf, symbol_type *sym, size_t length)
 
 void decode_md5 (unsigned char *tlvbuf, symbol_type *sym, size_t length)
 {
-  int j=0;
+  size_t j=0;
   if (length != 16 ) {
         printf("md5digest length mismatch!\n");
         exit(-45);