b43: Enable PCI slow clock workaround, if needed.

Index: wireless-testing/drivers/net/wireless/b43/main.c
===================================================================
@@ -4187,12 +4187,15 @@ static int b43_wireless_core_init(struct
 			hf |= B43_HF_4318TSSI;
 		if (phy->radio_rev < 6)
 			hf |= B43_HF_VCORECALC;
 	}
 	if (sprom->boardflags_lo & B43_BFL_XTAL_NOSLOW)
 		hf |= B43_HF_DSCRQ; /* Disable slowclock requests from ucode. */
+	if ((bus->bustype == SSB_BUSTYPE_PCI) &&
+	    (bus->pcicore.dev->id.revision <= 10))
+		hf |= B43_HF_PCISCW; /* PCI slow clock workaround. */
 	b43_hf_write(dev, hf);
 
 	b43_set_retry_limits(dev, B43_DEFAULT_SHORT_RETRY_LIMIT,
 			     B43_DEFAULT_LONG_RETRY_LIMIT);
 	b43_shm_write16(dev, B43_SHM_SHARED, B43_SHM_SH_SFFBLIM, 3);
 	b43_shm_write16(dev, B43_SHM_SHARED, B43_SHM_SH_LFFBLIM, 2);