airspeed drivers: Start handlers stack fixes and start handler review

src/drivers/ets_airspeed/ets_airspeed.cpp

@@ -286,6 +286,9 @@ void	info();
 
 /**
  * Start the driver.
+ *
+ * This function only returns if the sensor is up and running
+ * or could not be detected successfully.
  */
 void
 start(int i2c_bus)

src/drivers/ets_airspeed/module.mk

@@ -36,6 +36,7 @@
 #
 
 MODULE_COMMAND		= ets_airspeed
-MODULE_STACKSIZE	= 2048
 
 SRCS			= ets_airspeed.cpp
+
+MODULE_STACKSIZE	= 1200

src/drivers/meas_airspeed/meas_airspeed.cpp

@@ -420,6 +420,9 @@ void	info();
 
 /**
  * Start the driver.
+ *
+ * This function call only returns once the driver is up and running
+ * or failed to detect the sensor.
  */
 void
 start(int i2c_bus)

src/drivers/meas_airspeed/module.mk

@@ -36,6 +36,7 @@
 #
 
 MODULE_COMMAND		= meas_airspeed
-MODULE_STACKSIZE	= 2048
 
 SRCS			= meas_airspeed.cpp
+
+MODULE_STACKSIZE	= 1200