egk-tool: fixed reading relative files

adds compatibility with eGK 2.1
https://fachportal.gematik.de/fachportal-import/files/gemSpec_eGK_ObjSys_G2_1_V4.5.0.pdf

fixes OpenSC#2861

src/tools/egk-tool.c

@@ -177,7 +177,7 @@ main (int argc, char **argv)
 		goto err;
 
 	if (cmdline.pd_flag
-			&& read_file(card, "D001", &data, &data_len)
+			&& read_file(card, "iD001", &data, &data_len)
 			&& data_len >= 2) {
 		size_t len_pd = (data[0] << 8) | data[1];
 
@@ -195,7 +195,7 @@ main (int argc, char **argv)
 	}
 
 	if ((cmdline.vd_flag || cmdline.gvd_flag)
-			&& read_file(card, "D002", &data, &data_len)
+			&& read_file(card, "iD002", &data, &data_len)
 			&& data_len >= 8) {
 		size_t off_vd  = (data[0] << 8) | data[1];
 		size_t end_vd  = (data[2] << 8) | data[3];
@@ -230,7 +230,7 @@ main (int argc, char **argv)
 	}
 
 	if (cmdline.vsd_status_flag
-			&& read_file(card, "D00C", &data, &data_len)
+			&& read_file(card, "iD00C", &data, &data_len)
 			&& data_len >= 25) {
 		char *status;
 		unsigned int major, minor, fix;