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

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

BugLink: https://bugs.launchpad.net/bugs/1908561
[ Upstream commit c7eb900f5f45eeab1ea1bed997a2a12d8b5907bc ]

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.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Ian May <ian.may@canonical.com>