fix comment typo in pci-dma.c

Signed-off-by: Justin P. Mattock <justinmattock@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

arch/x86/kernel/pci-dma.c

@@ -38,7 +38,7 @@ int iommu_detected __read_mostly = 0;
  * This variable becomes 1 if iommu=pt is passed on the kernel command line.
  * If this variable is 1, IOMMU implementations do no DMA translation for
  * devices and allow every device to access to whole physical memory. This is
- * useful if a user want to use an IOMMU only for KVM device assignment to
+ * useful if a user wants to use an IOMMU only for KVM device assignment to
  * guests and not for driver dma translation.
  */
 int iommu_pass_through __read_mostly;