drm/i915/skl: Fix big integer constant sparse warning

intel_ddi.c:955:41: sparse: constant 8400000000 is so big it is long
intel_ddi.c:955:53: sparse: constant 9000000000 is so big it is long
intel_ddi.c:955:65: sparse: constant 9600000000 is so big it is long
intel_ddi.c:1028:23: sparse: constant 9600000000 is so big it is long
intel_ddi.c:1031:23: sparse: constant 9000000000 is so big it is long
intel_ddi.c:1034:23: sparse: constant 8400000000 is so big it is long

Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>