staging: vc04_services: Add helpers for vchiq driver data

Add helpers to set and get vchiq driver data. vchiq_set_drvdata() and
vchiq_get_drvdata() wraps dev_set_drvdata() and dev_get_drvdata()
respectively.

Signed-off-by: Umang Jain <umang.jain@ideasonboard.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>