x86, gart: Rename pci-gart_64.c to amd_gart_64.c

This file only contains code relevant for the northbridge
gart in AMD processors. This patch renames the file to
represent this fact in the filename.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index 7338ef2..97ebf82e 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -117,7 +117,7 @@
 ifeq ($(CONFIG_X86_64),y)
 	obj-$(CONFIG_AUDIT)		+= audit_64.o
 
-	obj-$(CONFIG_GART_IOMMU)	+= pci-gart_64.o aperture_64.o
+	obj-$(CONFIG_GART_IOMMU)	+= amd_gart_64.o aperture_64.o
 	obj-$(CONFIG_CALGARY_IOMMU)	+= pci-calgary_64.o tce_64.o
 	obj-$(CONFIG_AMD_IOMMU)		+= amd_iommu_init.o amd_iommu.o