drm/i915/drv: use intel_uncore_write() for register access

The implicit "dev_priv" local variable use has been a long-standing pain
point in the register access macros I915_READ(), I915_WRITE(),
POSTING_READ(), I915_READ_FW(), and I915_WRITE_FW().

Replace the sole remaining I915_WRITE() in i915_drv.c with
intel_uncore_write(), although it might be better to keep the entire
file void of direct register access.

No functional changes.
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200225111509.21879-3-jani.nikula@intel.com

drivers/gpu/drm/i915/i915_drv.c

@@ -763,7 +763,8 @@ static void i915_driver_register(struct drm_i915_private *dev_priv)
 	 * when running inside a VM.
 	 */
 	if (intel_vgpu_active(dev_priv))
-		I915_WRITE(vgtif_reg(display_ready), VGT_DRV_DISPLAY_READY);
+		intel_uncore_write(&dev_priv->uncore, vgtif_reg(display_ready),
+				   VGT_DRV_DISPLAY_READY);
 
 	/* Reveal our presence to userspace */
 	if (drm_dev_register(dev, 0) == 0) {