drm/i915: Add a way to test the modeset done during gpu reset, v3.

Add force_reset_modeset_test as a parameter to force the modeset path during gpu reset.
This allows a IGT test to set the knob and trigger a hang to force the gpu reset,
even on platforms that wouldn't otherwise require it.

Changes since v1:
- Split out fix to separate commit.
Changes since v2:
- This commit is purely about force_reset_modeset_test now.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Testcase: drv_hangman.reset-with-forced-modeset
Tested-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1470428910-12125-3-git-send-email-ville.syrjala@linux.intel.com
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

drivers/gpu/drm/i915/i915_params.c

@@ -45,6 +45,7 @@ struct i915_params i915 __read_mostly = {
 	.fastboot = 0,
 	.prefault_disable = 0,
 	.load_detect_test = 0,
+	.force_reset_modeset_test = 0,
 	.reset = true,
 	.invert_brightness = 0,
 	.disable_display = 0,
@@ -161,6 +162,11 @@ MODULE_PARM_DESC(load_detect_test,
 	"Force-enable the VGA load detect code for testing (default:false). "
 	"For developers only.");
 
+module_param_named_unsafe(force_reset_modeset_test, i915.force_reset_modeset_test, bool, 0600);
+MODULE_PARM_DESC(force_reset_modeset_test,
+	"Force a modeset during gpu reset for testing (default:false). "
+	"For developers only.");
+
 module_param_named_unsafe(invert_brightness, i915.invert_brightness, int, 0600);
 MODULE_PARM_DESC(invert_brightness,
 	"Invert backlight brightness "