ibmvnic: Fixes for check failover_pending

Description: Fix for the ibmvnic driver crash while accessing login buffer response if another failover happened.

Bugzilla: http://bugzilla.redhat.com/2010612

Build Info: https://brewweb.engineering.redhat.com/brew/taskinfo?taskID=41561363

Tested: Successfully tested by IBM. Sanity boot tested on power 9 (ibm-p9z-23-lp6) system.

Signed-off-by: Steve Best sbest@redhat.com