drm/connector: Add pixel clock to cmdline mode

We'll need to get the pixel clock to generate proper display modes for
all the current named modes. Let's add it to struct drm_cmdline_mode and
fill it when parsing the named mode.

Reviewed-by: Noralf Trønnes <noralf@tronnes.org>
Tested-by: Mateusz Kwiatkowski <kfyatek+publicgit@gmail.com>
Link: https://lore.kernel.org/r/20220728-rpi-analog-tv-properties-v9-12-24b168e5bcd5@cerno.tech
Signed-off-by: Maxime Ripard <maxime@cerno.tech>

include/drm/drm_connector.h

@@ -1212,6 +1212,13 @@ struct drm_cmdline_mode {
 	 */
 	bool bpp_specified;
 
+	/**
+	 * @pixel_clock:
+	 *
+	 * Pixel Clock in kHz. Optional.
+	 */
+	unsigned int pixel_clock;
+
 	/**
 	 * @xres:
 	 *