iommu/vt-d: Move intel_iommu_gfx_mapped to Intel IOMMU header

Static analyzer is not happy about intel_iommu_gfx_mapped declaration:

.../drivers/iommu/intel/iommu.c:364:5: warning: symbol 'intel_iommu_gfx_mapped' was not declared. Should it be static?

Move its declaration to Intel IOMMU header file.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Link: https://lore.kernel.org/r/20200828161212.71294-1-andriy.shevchenko@linux.intel.comSigned-off-by: Joerg Roedel <jroedel@suse.de>

include/drm/intel-gtt.h

@@ -5,6 +5,7 @@
 #define	_DRM_INTEL_GTT_H
 
 #include <linux/agp_backend.h>
+#include <linux/intel-iommu.h>
 #include <linux/kernel.h>
 
 void intel_gtt_get(u64 *gtt_total,
@@ -33,8 +34,4 @@ void intel_gtt_clear_range(unsigned int first_entry, unsigned int num_entries);
 /* flag for GFDT type */
 #define AGP_USER_CACHED_MEMORY_GFDT (1 << 3)
 
-#ifdef CONFIG_INTEL_IOMMU
-extern int intel_iommu_gfx_mapped;
-#endif
-
 #endif

include/linux/intel-iommu.h

@@ -792,6 +792,7 @@ extern int iommu_calculate_max_sagaw(struct intel_iommu *iommu);
 extern int dmar_disabled;
 extern int intel_iommu_enabled;
 extern int intel_iommu_tboot_noforce;
+extern int intel_iommu_gfx_mapped;
 #else
 static inline int iommu_calculate_agaw(struct intel_iommu *iommu)
 {