Fix buffer overflow in Marvell PCI/PCIe driver

Buffer overflow occured when more than one MSI was allocated.

Submitted by:    Wojciech Macek <wma@semihalf.com>
Obtained from:   Semihalf


git-svn-id: svn+ssh://svn.freebsd.org/base/head@275583 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f