drm/tegra: gem: Return 64-bit offset for mmap(2)

On 64-bit targets, tegra_gem_mmap() only returns a partial offset to
userspace. As such, subsequent calls to mmap(2) may fail. Change the
arguments to use a 64-bit offset to fix this.
Signed-off-by: NSean Paul <seanpaul@chromium.org>
Acked-by: NErik Faye-Lund <kusmabite@gmail.com>
[treding@nvidia.com: tweak commit message]
Signed-off-by: NThierry Reding <treding@nvidia.com>

include/uapi/drm/tegra_drm.h

@@ -36,7 +36,8 @@ struct drm_tegra_gem_create {
 
 struct drm_tegra_gem_mmap {
 	__u32 handle;
-	__u32 offset;
+	__u32 pad;
+	__u64 offset;
 };
 
 struct drm_tegra_syncpt_read {