drm/tegra: Allow compile test on !ARM v2

This compile tests on x86 just perfectly fine.

v2: fix missing include complained by kernel test robot

Signed-off-by: Christian König <christian.koenig@amd.com>
CC: Thierry Reding <thierry.reding@gmail.com>
CC: Jonathan Hunter <jonathanh@nvidia.com>
CC: linux-tegra@vger.kernel.org
Signed-off-by: Thierry Reding <treding@nvidia.com>