iommu/vt-d: Cleanup intel_context_flush_present()

iommu/vt-d: Cleanup intel_context_flush_present()

The intel_context_flush_present() is called in places where either the
scalable mode is disabled, or scalable mode is enabled but all PASID
entries are known to be non-present. In these cases, the flush_domains
path within intel_context_flush_present() will never execute. This dead
code is therefore removed.

Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Tested-by: Zhangfei Gao <zhangfei.gao@linaro.org>
Link: https://lore.kernel.org/r/20250228092631.3425464-7-baolu.lu@linux.intel.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>