Write io memory to clean PCIe buffer only when PCIe device is
present else this results into crash because of invalid memory
access.

Cc: <stable@vger.kernel.org> # 3.9+
Signed-off-by: NAvinash Patil <patila@marvell.com>
Signed-off-by: NBing Zhao <bzhao@marvell.com>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>