iommu/vt-d: Increase buffer size for device name

GCC is not happy with the current code, e.g.:

.../iommu/intel/dmar.c:1063:9: note: ‘sprintf’ output between 6 and 15 bytes into a destination of size 13
 1063 |         sprintf(iommu->name, "dmar%d", iommu->seq_id);

When `make W=1` is supplied, this prevents kernel building. Fix it by
increasing the buffer size for device name and use sizeoF() instead of
hard coded constants.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20241014104529.4025937-1-andriy.shevchenko@linux.intel.com


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