fix capitalisation of include file name

Marko Pagott <p0rc0.jet@gmail.com>
Hotfix: Wrong capitalization on header file name
Hotfix: Wrong capitalization on header file name
Merge branch 'master' of github.com:PX4/Firmware
Merge branch 'master' into new_led_status
Tested with PX4FMU and PX4IO with GPS and arming