x86/gart: Unexport gart_iommu_aperture

I wrongly exported gart_iommu_aperture in the commit
42590a75. It's not necessary so
let's unexport it.
Signed-off-by: NFUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: Joerg Roedel <joerg.roedel@amd.com>
LKML-Reference: <20100215113241P.fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

arch/x86/kernel/aperture_64.c

@@ -31,7 +31,6 @@
 #include <asm/x86_init.h>
 
 int gart_iommu_aperture;
-EXPORT_SYMBOL_GPL(gart_iommu_aperture);
 int gart_iommu_aperture_disabled __initdata;
 int gart_iommu_aperture_allowed __initdata;