ibmvnic: reduce wait for completion time

Reduce the wait time for Command Response Queue response from 30 seconds
to 20 seconds, as recommended by VIOS and Power Hypervisor teams.

Fixes: bd0b6723 ("ibmvnic: Move login and queue negotiation into ibmvnic_open")
Fixes: 53da09e9

 ("ibmvnic: Add set_link_state routine for setting adapter link state")
Signed-off-by: Dany Madden <drt@linux.ibm.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>