drm/tegra: Depend on COMMON_CLK

The introduction of the COMPILE_TEST dependency in commit 158b50ae
(drm/tegra: Increase compile test coverage) removes the dependency on
COMMON_CLK (implicitly selected via ARCH_TEGRA, ARCH_MULTI_V7 and
ARCH_MULTIPLATFORM).

Reported-by: Russell King <linux@arm.linux.org.uk>
Signed-off-by: Thierry Reding <treding@nvidia.com>