drm/i915: Don't compare has_drrs strictly in pipe config

The commit [cfb23ed: drm/i915: Allow fuzzy matching in
pipe_config_compare, v2] relaxed the way to compare the pipe
configurations, but one new comparison sneaked in there: it added the
strict has_drrs value check.  This causes a regression on many
machines, typically HP laptops with a docking port, where the kernel
spews warnings and eventually fails to set the mode properly like:
 [drm:intel_pipe_config_compare [i915]] *ERROR* mismatch in has_drrs (expected 1, found 0)
 ------------[ cut here ]------------
 WARNING: CPU: 0 PID: 79 at drivers/gpu/drm/i915/intel_display.c:12700 intel_modeset_check_state+0x5aa/0x870 [i915]()
 pipe state doesn't match!
 ....

This patch just removes the check again for fixing the regression.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=104041
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=92456
Bugzilla: https://bugzilla.suse.com/show_bug.cgi?id=956397
Fixes: cfb23ed ('drm/i915: Allow fuzzy matching in pipe_config_compare, v2')
Cc: <stable@vger.kernel.org> # v4.3+
Reported-and-tested-by: Max Lin <mlin@suse.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1448461607-16868-1-git-send-email-tiwai@suse.de
Signed-off-by: Jani Nikula <jani.nikula@intel.com>

Author: tiwai

drivers/gpu/drm/i915/intel_display.c

@@ -12460,7 +12460,6 @@ intel_pipe_config_compare(struct drm_device *dev,
 	if (INTEL_INFO(dev)->gen < 8) {
 		PIPE_CONF_CHECK_M_N(dp_m_n);
 
-		PIPE_CONF_CHECK_I(has_drrs);
 		if (current_config->has_drrs)
 			PIPE_CONF_CHECK_M_N(dp_m2_n2);
 	} else