video: tegra-dc: pass DC regmap to internal devices

Internal video devices like DSI and HDMI controllers
require sending commands into DC register field.
To make this available, lets create platform data,
which is restricted to pass DC regmap only to
pre-defined devices.

Tested-by: Andreas Westman Dorcsak <hedmoo@yahoo.com> # ASUS TF T30
Tested-by: Nicolas Chauvet <kwizart@gmail.com> # Paz00
Tested-by: Robert Eckelmann <longnoserob@gmail.com> # ASUS TF101 T20
Tested-by: Svyatoslav Ryhel <clamor95@gmail.com> # HTC One X T30
Signed-off-by: Svyatoslav Ryhel <clamor95@gmail.com>