iommu/vt-d: Remove unused dmar_msi_read

dmar_msi_read() has been unused since 2022 in
commit cf8e8658 ("arch: Remove Itanium (IA-64) architecture")

Remove it.

(dmar_msi_write still exists and is used once).

Signed-off-by: Dr. David Alan Gilbert <linux@treblig.org>
Link: https://lore.kernel.org/r/20241022002702.302728-1-linux@treblig.org


Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>