Add host1x, the driver for host1x and its client unit 2D. The Tegra
host1x module is the DMA engine for register access to Tegra's
graphics- and multimedia-related modules. The modules served by
host1x are referred to as clients. host1x includes some other
functionality, such as synchronization.

Signed-off-by: Arto Merilainen
Signed-off-by: Terje Bergstrom
Reviewed-by: Thierry Reding
Tested-by: Thierry Reding
Tested-by: Erik Faye-Lund
Signed-off-by: Thierry Reding