drm/i915: Disable intel_gmch_probe() and intel_enable_gtt()

They are now no-ops, like they are in `drm2` in FreeBSD base.

They were used by Intel GPUs up to and including gen 5. This patch makes
the driver work on those old Intel GPUs. At least it was successfully
tested on an Intel 965GM coupled with an Intel Core 2 Duo from 2007.

Author: dumbbell

drivers/gpu/drm/i915/intel_freebsd.c

@@ -33,17 +33,20 @@ uint32_t intel_gtt_read_pte(unsigned int entry);
 
 #define WARN_UN() log(LOG_WARNING, "%s unimplemented", __FUNCTION__)
 
+#ifdef __notyet__
 static struct _intel_private {
 	struct pci_dev *bridge_dev;
 	u8 __iomem *registers;
 	u32 PGTBL_save;
 	int gen;
 	phys_addr_t gma_bus_addr;
 } intel_private;
+#endif
 
 bool
 intel_enable_gtt(void)
 {
+#ifdef __notyet__
 	u8 __iomem *reg;
 
 	DRM_DEBUG("entering %s\n", __func__);
@@ -90,13 +93,15 @@ intel_enable_gtt(void)
 	if (INTEL_GTT_GEN >= 3)
 		writel(0, intel_private.registers + GFX_FLSH_CNTL_BSD);
 	DRM_DEBUG("exiting %s\n", __func__);
+#endif
 	return (1);
 }
 
 int
 intel_gmch_probe(struct pci_dev *bridge_pdev, struct pci_dev *gpu_pdev,
 		 struct agp_bridge_data *bridge)
 {
+#ifdef __notyet__
 	DRM_DEBUG("entering %s\n", __func__);
 	intel_private.registers = NULL; //intel_gtt_get_registers();
 	intel_private.gma_bus_addr = pci_bus_address(gpu_pdev, I915_GMADR_BAR);
@@ -111,6 +116,7 @@ intel_gmch_probe(struct pci_dev *bridge_pdev, struct pci_dev *gpu_pdev,
 		intel_private.PGTBL_save |= AGP_I810_PGTBL_ENABLED;
 
 	DRM_DEBUG("exiting %s\n", __func__);
+#endif
 	return (1);
 }