drm/i915: s/is_sdvob/enum port/

Replace the is_sdvob bool and some sdvo_reg checks with enum port. This
makes the SDVO code look more modern, and gets rid of explicit register
offset checks in the code which will hamper register type checking.

v2: Add assert_sdvo_port_valid() (Chris)

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: http://patchwork.freedesktop.org/patch/msgid/1446838199-3666-1-git-send-email-ville.syrjala@linux.intel.com

drivers/gpu/drm/i915/intel_drv.h

@@ -1465,7 +1465,7 @@ void skl_ddb_get_hw_state(struct drm_i915_private *dev_priv,
 uint32_t ilk_pipe_pixel_rate(const struct intel_crtc_state *pipe_config);
 
 /* intel_sdvo.c */
-bool intel_sdvo_init(struct drm_device *dev, uint32_t sdvo_reg, bool is_sdvob);
+bool intel_sdvo_init(struct drm_device *dev, uint32_t sdvo_reg, enum port port);
 
 
 /* intel_sprite.c */