[rbp/omxplayer] Fixed: analog output was not properly enabled 

@popcornmix: the RPi analog output was not properly enabled due to a case sensitive settings check.

Commit 67e957df from @FernetMenta changed the driver name from "Pi" to "PI".

As a result, the audiodevice name in the guisettings.xml becomes "PI:Analogue".
Due to the case mismatch, the analogue output was never enabled without manually changing the name back to "Pi:Analogue" in the guisettings.xml.