Remove i810_drm.h and i830_drm.h from the distribution tarball

Both of these headers are not installed since they were imported.
They  are not even used internally. The latter no longer exist in the
kernel...

Note the * symbol in EXTRA_DIST causes 'make distcheck' to fail. When
was the last time we ran it ?

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Damien Lespiau <damien.lespiau@intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
Reviewed-by: Jakob Bornecrantz <jakob@vmware.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>