AMD IOMMU: remove unnecessary cast to u64 in the init code

The ctrl variable is only u32 and readl also returns a 32 bit value. So
the cast to u64 is pointless. Remove it with this patch.
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/kernel/amd_iommu_init.c

@@ -235,7 +235,7 @@ static void __init iommu_feature_disable(struct amd_iommu *iommu, u8 bit)
 {
 	u32 ctrl;
 
-	ctrl = (u64)readl(iommu->mmio_base + MMIO_CONTROL_OFFSET);
+	ctrl = readl(iommu->mmio_base + MMIO_CONTROL_OFFSET);
 	ctrl &= ~(1 << bit);
 	writel(ctrl, iommu->mmio_base + MMIO_CONTROL_OFFSET);
 }