ssb: fix PCI(e) driver regression causing oops on PCI cards

We were incorrectly executing PCIe specific workarounds on PCI cards.
This resulted in:
Machine check in kernel mode.
Caused by (from SRR1=149030): Transfer error ack signal
Oops: Machine check, sig: 7 [#1]

Reported-by: Andreas Schwab <schwab@linux-m68k.org>
Signed-off-by: Rafał Miłecki <zajec5@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>