BoardConfig.mk: use TARGET_DEVICE

Use TARGET_DEVICE as filter instead TARGET_PRODUCT to allow compileing
PhilZ Touch on different Rom Sources.
Merge pull request #59 from andi34/pull

BoardConfig.mk: use TARGET_DEVICE
Merge remote-tracking branch 'philz/cm-11.0-beta' into cm-11.0-beta
- GTab to TARGET_DEVICE