iommu/vt-d: Remove initialization for dynamically heap-allocated rcu_head

The rcu_head structures allocated dynamically in the heap don't need any
initialization. Therefore, remove the init_rcu_head().

Signed-off-by: Tina Zhang <tina.zhang@intel.com>
Link: https://lore.kernel.org/r/20240219125723.1645703-3-tina.zhang@intel.com


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