GetTargetVoltage: Print info about voltage only when info is relevant.

src/command.c

@@ -171,7 +171,8 @@ static bool cmd_jtag_scan(target *t, int argc, char **argv)
 	(void)t;
 	uint8_t irlens[argc];
 
-	gdb_outf("Target voltage: %s\n", platform_target_voltage());
+	if (platform_target_voltage())
+		gdb_outf("Target voltage: %s\n", platform_target_voltage());
 
 	if (argc > 1) {
 		/* Accept a list of IR lengths on command line */
@@ -216,7 +217,8 @@ bool cmd_swdp_scan(target *t, int argc, char **argv)
 	(void)t;
 	(void)argc;
 	(void)argv;
-	gdb_outf("Target voltage: %s\n", platform_target_voltage());
+	if (platform_target_voltage())
+		gdb_outf("Target voltage: %s\n", platform_target_voltage());
 
 	if(connect_assert_srst)
 		platform_srst_set_val(true); /* will be deasserted after attach */

src/platforms/f4discovery/platform.c

@@ -100,7 +100,7 @@ bool platform_srst_get_val(void) { return false; }
 
 const char *platform_target_voltage(void)
 {
-	return "ABSENT!";
+	return NULL;
 }
 
 void platform_request_boot(void)

src/platforms/hydrabus/platform.c

@@ -85,7 +85,7 @@ bool platform_srst_get_val(void) { return false; }
 
 const char *platform_target_voltage(void)
 {
-	return "ABSENT!";
+	return NULL;
 }
 
 void platform_request_boot(void)

src/platforms/launchpad-icdi/platform.c

@@ -115,7 +115,7 @@ void platform_delay(uint32_t ms)
 
 const char *platform_target_voltage(void)
 {
-	return "not supported";
+	return NULL;
 }
 
 char *serialno_read(char *s)

src/platforms/pc/cl_utils.c

@@ -272,7 +272,8 @@ int cl_execute(BMP_CL_OPTIONS_t *opt)
 	platform_srst_set_val(opt->opt_connect_under_reset);
 	if (opt->opt_mode == BMP_MODE_TEST)
 		printf("Running in Test Mode\n");
-	printf("Target voltage: %s Volt\n", platform_target_voltage());
+	if (platform_target_voltage())
+		printf("Target voltage: %s Volt\n", platform_target_voltage());
 	if (opt->opt_usejtag) {
 		num_targets = platform_jtag_scan(NULL);
 	} else {

src/platforms/swlink/platform.c

@@ -177,7 +177,7 @@ const char *platform_target_voltage(void)
 		ret[2] = '0' + val_in_100mV % 10;
 		return ret;
 	}
-	return "ABSENT!";
+	return NULL;
 }
 
 void set_idle_state(int state)