drm/i915: Grammar s/the its/its/

Fix the grammar.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190607113118.14645-1-geert+renesas@glider.be

drivers/gpu/drm/i915/intel_dpll_mgr.h

@@ -293,7 +293,7 @@ struct intel_shared_dpll {
 	/**
 	 * @state:
 	 *
-	 * Store the state for the pll, including the its hw state
+	 * Store the state for the pll, including its hw state
 	 * and CRTCs using it.
 	 */
 	struct intel_shared_dpll_state state;