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 <[e-mail]>
Reviewed-by: Lu Baolu <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Joerg Roedel <[e-mail]>

include/drm/intel-gtt.h

···
 #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,
···
 
 /* 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

···
 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)
 {