bitvec: bitvec_to_string_r(): drop unused variable

bitvec.c:543:14: warning: variable 'pos' set but not used [-Wunused-but-set-variable]
        unsigned i, pos = 0;

Change-Id: I17df6f9263bee06676309c00837f12220803c814
diff --git a/src/core/bitvec.c b/src/core/bitvec.c
index 38ea1bb..ac702b9 100644
--- a/src/core/bitvec.c
+++ b/src/core/bitvec.c
@@ -540,13 +540,11 @@
  */
 void bitvec_to_string_r(const struct bitvec *bv, char *str)
 {
-	unsigned i, pos = 0;
 	char *cur = str;
-	for (i = 0; i < bv->cur_bit; i++) {
+	for (unsigned int i = 0; i < bv->cur_bit; i++) {
 		if (0 == i % 8)
 			*cur++ = ' ';
 		*cur++ = bit_value_to_char(bitvec_get_bit_pos(bv, i));
-		pos++;
 	}
 	*cur = 0;
 }