drivers: Fix compile warnings and non-standard performance counter names

src/drivers/mpu6000/mpu6000.cpp

@@ -1380,7 +1380,6 @@ MPU6000_gyro::init()
 
 	_gyro_class_instance = register_class_devname(GYRO_DEVICE_PATH);
 
-out:
 	return ret;
 }
 

src/drivers/ms5611/ms5611.cpp

@@ -753,8 +753,8 @@ MS5611::print_info()
 	printf("TEMP:           %d\n", _TEMP);
 	printf("SENS:           %lld\n", _SENS);
 	printf("OFF:            %lld\n", _OFF);
-	printf("P:              %.3f\n", _P);
-	printf("T:              %.3f\n", _T);
+	printf("P:              %.3f\n", (double)_P);
+	printf("T:              %.3f\n", (double)_T);
 	printf("MSL pressure:   %10.4f\n", (double)(_msl_pressure / 100.f));
 
 	printf("factory_setup             %u\n", _prom.factory_setup);

src/drivers/px4io/px4io_serial.cpp

@@ -639,7 +639,7 @@ PX4IO_serial::_do_interrupt()
 		if (_rx_dma_status == _dma_status_waiting) {
 
 			/* verify that the received packet is complete */
-			unsigned length = sizeof(_dma_buffer) - stm32_dmaresidual(_rx_dma);
+			int length = sizeof(_dma_buffer) - stm32_dmaresidual(_rx_dma);
 			if ((length < 1) || (length < PKT_SIZE(_dma_buffer))) {
 				perf_count(_pc_badidle);
 

src/drivers/sf0x/sf0x.cpp

@@ -254,9 +254,6 @@ SF0X::~SF0X()
 int
 SF0X::init()
 {
-	int ret = ERROR;
-	unsigned i = 0;
-
 	/* do regular cdev init */
 	if (CDev::init() != OK) {
 		goto out;
@@ -594,7 +591,7 @@ SF0X::collect()
 		valid = false;
 
 		/* wipe out partially read content from last cycle(s), check for dot */
-		for (int i = 0; i < (lend - 2); i++) {
+		for (unsigned i = 0; i < (lend - 2); i++) {
 			if (_linebuf[i] == '\n') {
 				char buf[sizeof(_linebuf)];
 				memcpy(buf, &_linebuf[i+1], (lend + 1) - (i + 1));
@@ -795,7 +792,7 @@ const int ERROR = -1;
 
 SF0X	*g_dev;
 
-void	start();
+void	start(const char *port);
 void	stop();
 void	test();
 void	reset();

src/drivers/stm32/adc/adc.cpp

@@ -145,7 +145,7 @@ private:
 
 ADC::ADC(uint32_t channels) :
 	CDev("adc", ADC_DEVICE_PATH),
-	_sample_perf(perf_alloc(PC_ELAPSED, "ADC samples")),
+	_sample_perf(perf_alloc(PC_ELAPSED, "adc_samples")),
 	_channel_count(0),
 	_samples(nullptr),
 	_to_system_power(0)