fix display bug causing all the 'ff's

jni/evoplus_cid.c

@@ -44,7 +44,7 @@ int cid_backdoor(int fd) {
 	return ret;
 }
 
-int program_cid(int fd, char *cid) {
+int program_cid(int fd, const unsigned char *cid) {
 	int ret;
 	struct mmc_ioc_cmd idata = {0};
 
@@ -65,7 +65,7 @@ int program_cid(int fd, char *cid) {
 	return ret;
 }
 
-void show_cid(char *cid) {
+void show_cid(const unsigned char *cid) {
 	int i;
 	for (i = 0; i < CID_SIZE; i++){
 		printf("%02x", cid[i]);
@@ -73,7 +73,7 @@ void show_cid(char *cid) {
 	printf("\n");
 }
 
-unsigned char crc7(unsigned char data[], int len) {
+unsigned char crc7(const unsigned char data[], int len) {
 
 	int count;
 	unsigned char crc = 0;
@@ -116,7 +116,7 @@ int parse_serial(const char *str) {
 
 void main(int argc, const char **argv) {
 	int fd, ret, i, len;
-	char cid[CID_SIZE] = {0};
+	unsigned char cid[CID_SIZE] = {0};
 
 	if (argc != 3 && argc != 4) {
 		printf("Usage: ./evoplus_cid <device> <cid> [serial]\n");