intel-iommu: kill off duplicate def of dmar_disabled

This is only used in dmar.c and intel-iommu.h, so dma_remapping.h
seems like the appropriate place for it.
Signed-off-by: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

include/linux/dmar.h

@@ -144,7 +144,6 @@ struct dmar_rmrr_unit {
 	list_for_each_entry(rmrr, &dmar_rmrr_units, list)
 /* Intel DMAR  initialization functions */
 extern int intel_iommu_init(void);
-extern int dmar_disabled;
 #else
 static inline int intel_iommu_init(void)
 {