ssb: Clear RETRY_TIMEOUT in PCI Configuration for normal devices

MMIO log traces obtained using the Broadcom wl hybrid driver show that
the RETRY_TIMEOUT register (0x41) in PCI configuration space is cleared
if non-zero. Similar code found in other drivers such as ipw2100 show
this operation is needed to keep PCI Tx retries from interfering with
C3 CPU state. There are no known cases where omission of this code has
caused a problem, but this patch is offered just in case such a situation
occurs.

Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>