drm/i915: set default value for config->pixel_multiplier

This way we can simplify the code quite a bit.

Also add a WARN in the sdvo code to complain about a bogus value
and kill the readout code in intel_ddi.c that Jesse sneaked in.
HW state readout for the pixel multiplier will work a bit differently
in the end.

v2: Rebase on top of the fdi pixel mutliplier handling fix.

Reviewed-by: Imre Deak <imre.deak@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/intel_sdvo.c b/drivers/gpu/drm/i915/intel_sdvo.c
index 7068195..f4588a2 100644
--- a/drivers/gpu/drm/i915/intel_sdvo.c
+++ b/drivers/gpu/drm/i915/intel_sdvo.c
@@ -1219,6 +1219,7 @@
 
 	switch (intel_crtc->config.pixel_multiplier) {
 	default:
+		WARN(1, "unknown pixel mutlipler specified\n");
 	case 1: rate = SDVO_CLOCK_RATE_MULT_1X; break;
 	case 2: rate = SDVO_CLOCK_RATE_MULT_2X; break;
 	case 4: rate = SDVO_CLOCK_RATE_MULT_4X; break;