drm/i915/dsi: Fix chv_exec_gpio disabling the GPIOs it is setting

Set the CHV_GPIO_GPIOEN bit when updating GPIOs from chv_exec_gpio.

Fixes: a0a6d4f ("drm/i915/dsi: add support for gpio elements on CHV")
Cc: stable@vger.kernel.org
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20161201202925.12220-3-hdegoede@redhat.com
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
(cherry picked from commit b2b45fc)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>

drivers/gpu/drm/i915/intel_dsi_panel_vbt.c

@@ -300,7 +300,8 @@ static void chv_exec_gpio(struct drm_i915_private *dev_priv,
 	mutex_lock(&dev_priv->sb_lock);
 	vlv_iosf_sb_write(dev_priv, port, cfg1, 0);
 	vlv_iosf_sb_write(dev_priv, port, cfg0,
-			  CHV_GPIO_GPIOCFG_GPO | CHV_GPIO_GPIOTXSTATE(value));
+			  CHV_GPIO_GPIOEN | CHV_GPIO_GPIOCFG_GPO |
+			  CHV_GPIO_GPIOTXSTATE(value));
 	mutex_unlock(&dev_priv->sb_lock);
 }