drm/tegra: Fix build for Linux v6.14

In Linux v6.14, the 'date' field was removed from the 'drm_driver'
structure. Add a test to conftest to detect this and update the Tegra
DRM driver accordingly.

Jira LINQPJ14-6

Change-Id: Ia3024321f12f8448d382deba996407f9d3232567
Signed-off-by: Jon Hunter <jonathanh@nvidia.com>
Reviewed-on: https://git-master.nvidia.com/r/c/linux-nv-oot/+/3297069
(cherry picked from commit 12d50906f3800c37a35be59b49157797ed529159)
Reviewed-on: https://git-master.nvidia.com/r/c/linux-nv-oot/+/3499756
Reviewed-by: Brad Griffis <bgriffis@nvidia.com>
GVS: buildbot_gerritrpt <buildbot_gerritrpt@nvidia.com>
Tested-by: Brad Griffis <bgriffis@nvidia.com>

drivers/gpu/drm/tegra/drm.c

@@ -911,7 +911,9 @@ static const struct drm_driver tegra_drm_driver = {
 
 	.name = DRIVER_NAME,
 	.desc = DRIVER_DESC,
+#if defined(NV_DRM_DRIVER_STRUCT_HAS_DATE) /* Linux v6.14 */
 	.date = DRIVER_DATE,
+#endif
 	.major = DRIVER_MAJOR,
 	.minor = DRIVER_MINOR,
 	.patchlevel = DRIVER_PATCHLEVEL,