Compiler is not happy about hidden declaration of intel_iommu_ops.

.../iommu.c:414:24: warning: symbol 'intel_iommu_ops' was not declared. Should it be static?

Move declaration to header file to make compiler happy.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20220207141240.8253-1-andriy.shevchenko@linux.intel.comSigned-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Link: https://lore.kernel.org/r/20220301020159.633356-10-baolu.lu@linux.intel.comSigned-off-by: Joerg Roedel <jroedel@suse.de>