MAINTAINERS: Update Tegra DRM entry

Change email to my private address, point file entry to the new location
below drivers/gpu/host1x, add include/uapi/drm/tegra_drm.h to maintained
file list and update git tree.

Furthermore, Terje Bergström will be co-maintaining.

Signed-off-by: Thierry Reding <thierry.reding@gmail.com>