drivers: doxygen documentation improvement

drivers/include/adcxx1c.h

drivers/include/bmp180.h

drivers/include/bmx280.h

drivers/include/cc110x.h

drivers/include/cc2420.h

drivers/include/io1_xplained.h

drivers/include/led.h

drivers/include/mpu9150.h

drivers/include/sht11.h

drivers/include/si70xx.h

drivers/include/srf02.h

drivers/include/sx127x.h

drivers/include/tsl2561.h

drivers/include/veml6070.h

drivers/include/w5100.h

drivers/io1_xplained/include/io1_xplained_internals.h