phb4: Update link training documentation
We added degraded link retries in:
phb4: Retrain link if degraded
but forgot to update the documentation.
* o Once we leave here, much harder to recover from errors
*
* Step 9:
+ * - Check for optimised link for directly attached devices:
+ * o Wait for CRS (so we can read device config space)
+ * o Check chip and device are in whitelist. if not, Goto Step 10
+ * o If trained link speed is degraded, retry -> Goto Step 2
+ * o If trained link width is degraded, retry -> Goto Step 2
+ * o If still degraded after 3 retries. Give up, Goto Step 10.
+ *
+ * Step 10:
* - PHB good, start probing config space.
* o core/pci.c: pci_reset_phb() -> pci_scan_phb()
*/
