x86/amd-iommu: Un__init function required on shutdown

The function iommu_feature_disable is required on system
shutdown to disable the IOMMU but it is marked as __init.
This may result in a panic if the memory is reused. This
patch fixes this bug.
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>

arch/x86/kernel/amd_iommu_init.c

@@ -240,7 +240,7 @@ static void iommu_feature_enable(struct amd_iommu *iommu, u8 bit)
 	writel(ctrl, iommu->mmio_base + MMIO_CONTROL_OFFSET);
 }
 
-static void __init iommu_feature_disable(struct amd_iommu *iommu, u8 bit)
+static void iommu_feature_disable(struct amd_iommu *iommu, u8 bit)
 {
 	u32 ctrl;