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: Avinash Patil <patila@marvell.com>
Signed-off-by: Bing Zhao <bzhao@marvell.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>