i2c spi: add type to I2CSPIInstance

Needed to distinguish runtime instance types of the same driver (e.g.
bmi055 accel vs gyro).

Tools/px4moduledoc/srcparser.py

@@ -15,7 +15,8 @@ class ModuleDocumentation(object):
     # TOC in https://github.com/PX4/Devguide/blob/master/en/SUMMARY.md
     valid_categories = ['driver', 'estimator', 'controller', 'system',
                         'communication', 'command', 'template', 'simulation']
-    valid_subcategories = ['', 'distance_sensor']
+    valid_subcategories = ['', 'distance_sensor', 'imu', 'airspeed_sensor',
+                           'magnetometer', 'baro']
 
     max_line_length = 80 # wrap lines that are longer than this