drm/i915: Restore the preliminary HW check.

We still maintain code internally that cares about preliminary support.
Leaving the check here doesn't hurt anyone, and should keep things more
in line.

This time around, stick the info in the intel_info structure, and also
change the error from DRM_ERROR->DRM_INFO.

This is a partial revert of:
commit 590e4df
Author: Jesse Barnes <jbarnes@virtuousgeek.org>
Date:   Wed May 8 10:45:15 2013 -0700

    drm/i915: VLV support is no longer preliminary

Daniel, I'll provide the fix ups for internal too if/when you merge
this (if you want).

Cc: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Ben Widawsky <ben@bwidawsk.net>
Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_drv.c

@@ -799,6 +799,12 @@ static int i915_pci_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
 	struct intel_device_info *intel_info =
 		(struct intel_device_info *) ent->driver_data;
 
+	if (IS_PRELIMINARY_HW(intel_info) && !i915_preliminary_hw_support) {
+		DRM_INFO("This hardware requires preliminary hardware support.\n"
+			 "See CONFIG_DRM_I915_PRELIMINARY_HW_SUPPORT, and/or modparam preliminary_hw_support\n");
+		return -ENODEV;
+	}
+
 	/* Only bind to function 0 of the device. Early generations
 	 * used function 1 as a placeholder for multi-head. This causes
 	 * us confusion instead, especially on the systems where both

drivers/gpu/drm/i915/i915_drv.h

@@ -420,6 +420,7 @@ struct intel_uncore {
 	func(is_ivybridge) sep \
 	func(is_valleyview) sep \
 	func(is_haswell) sep \
+	func(is_preliminary) sep \
 	func(has_force_wake) sep \
 	func(has_fbc) sep \
 	func(has_pipe_cxsr) sep \
@@ -1605,6 +1606,7 @@ struct drm_i915_file_private {
 				 ((dev)->pci_device & 0xFF00) == 0x0A00)
 #define IS_HSW_GT3(dev)		(IS_HASWELL(dev) && \
 				 ((dev)->pci_device & 0x00F0) == 0x0020)
+#define IS_PRELIMINARY_HW(intel_info) ((intel_info)->is_preliminary)
 
 /*
  * The genX designation typically refers to the render engine, so render