r8152: Factor out OOB link list waits

The same for-loop check for the LINK_LIST_READY bit of an OOB_CTRL
register is used in several places. Factor these out into a single
function to reduce the lines of code.

Change-Id: I20e8f327045a72acc0a83e2d145ae2993ab62915
Signed-off-by: Prashant Malani <pmalani@chromium.org>
Reviewed-by: Grant Grundler <grundler@chromium.org>
Acked-by: Hayes Wang <hayeswang@realtek.com>
Signed-off-by: David S. Miller <davem@davemloft.net>