For Cannonlake the number of scalers for each pipe is 2. Let's increase
the number of scalers for pipe C.

v2: Use INTEL_GEN() instead of IS_CANNONLAKE()
Signed-off-by: Mika Kahola <mika.kahola@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/1509530930-24960-1-git-send-email-mika.kahola@intel.com