Remove MSI IRQ storms prevention logic

Remove MSI IRQ storms prevention logic

The reason is:
1. The logic has negative impact on 10G NIC performance (assigned to
guest) by lowering the interrupt frequency that Xen can handle.
2. Xen already has IRQ rate limit logic, which can also help to
prevent IRQ storms.

Signed-off-by: Shan Haitao <haitao.shan@intel.com>