shell: fix printing hex when size is larger than 16

shell.c

@@ -57,19 +57,21 @@ static void parse_hex(FILE *fp, char *buf, size_t len)
 
 static void print_hex_ascii(FILE *fp, const char *buf, size_t len)
 {
-	size_t i, j;
+	size_t n, i;
 	char c;
 
-	for (j = 0; j < len; j += 16, buf += 16) {
+	for (; len; buf += n, len -= n) {
+		n = min(len, 16);
+		
 		for (i = 0; i < 16; ++i) {
-			c = (i < len) ? buf[i] : 0;
+			c = (i < n) ? buf[i] : 0;
 			fprintf(fp, "%02x", c);
 		}
 
 		fprintf(fp, " ");
 
 		for (i = 0; i < 16; ++i) {
-			c = (i < len) ? buf[i] : 0;
+			c = (i < n) ? buf[i] : 0;
 			fprintf(fp, "%c", isalnum(c) ? c : '.');
 		}