In some case reading root switch config space takes longer than what we
are currently waiting in the driver resulting timeout and failure.
Increase number of retries to allow some more time for the root switch
config space to become accesssible.

Also log an error if the timeout is exceeded so we know why the driver
probe failed.
Signed-off-by: NMika Westerberg <mika.westerberg@linux.intel.com>
Reviewed-by: NAndy Shevchenko <andy.shevchenko@gmail.com>