Implement support for the VBLANK IOCTL. Note that Tegra is somewhat
special in this case because it doesn't use the generic IRQ support
provided by the DRM core (DRIVER_HAVE_IRQ) but rather registers one
interrupt handler for each display controller.

While at it, clean up the way that interrupts are enabled to ensure
that the VBLANK interrupt only gets enabled when required.
Signed-off-by: NThierry Reding <thierry.reding@avionic-design.de>

This commit adds a KMS driver for the Tegra20 SoC. This includes basic
support for host1x and the two display controllers found on the Tegra20
SoC. Each display controller can drive a separate RGB/LVDS output.
Signed-off-by: NThierry Reding <thierry.reding@avionic-design.de>
Tested-by: NStephen Warren <swarren@nvidia.com>
Acked-by: NMark Zhang <markz@nvidia.com>
Reviewed-by: NMark Zhang <markz@nvidia.com>
Tested-by: NMark Zhang <markz@nvidia.com>
Tested-and-acked-by: NAlexandre Courbot <acourbot@nvidia.com>
Acked-by: NTerje Bergstrom <tbergstrom@nvidia.com>
Tested-by: NTerje Bergstrom <tbergstrom@nvidia.com>
Signed-off-by: NDave Airlie <airlied@redhat.com>