drm/tegra: Remove superfluous error messages around platform_get_irq()

The platform_get_irq() prints error message telling that interrupt is
missing,hence there is no need to duplicated that message in the
drivers.

Signed-off-by: Tan Zhongjun <tanzhongjun@yulong.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>