drm/tegra: plane: Improve use of dev_err_probe()

Return dev_err_probe() directly, because the return value of
dev_err_probe() is the appropriate error code, and it can
reduce code size, simplify the code.

Signed-off-by: Cai Huoqing <caihuoqing@baidu.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>