Fix GPE check on init

Many (or all) GPE devices do not use mmcblk0p36 for /data

thanks to Rhyn for spotting this

Change-Id: I55be45a08b7dfad23f7d3ab37ed40263634778a5
init: Use userdata by name to detect GPE

Change-Id: I563236c25b151a51522adc81b8498fdb8bd9b1f3