drm/i915: fixup assert_pipe to take the pipe A quirk into account

This was completely spamming dmesg on my i855gm. This issue was just
shortly introduced with:

commit 931872fc
Author: Chris Wilson <chris@chris-wilson.co.uk>
Date:   Mon Jan 16 23:01:13 2012 +0000

    drm/i915: Check that plane/pipe is disabled before removing the fb
Reviewed-by: NJesse Barnes <jbarnes@virtuousgeek.org>
Signed-Off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_display.c

@@ -936,6 +936,10 @@ void assert_pipe(struct drm_i915_private *dev_priv,
 	u32 val;
 	bool cur_state;
 
+	/* if we need the pipe A quirk it must be always on */
+	if (pipe == PIPE_A && dev_priv->quirks & QUIRK_PIPEA_FORCE)
+		state = true;
+
 	reg = PIPECONF(pipe);
 	val = I915_READ(reg);
 	cur_state = !!(val & PIPECONF_ENABLE);