mlxsw: pci: Remove unused wait queue

The previous patch changed the code to do not handle command interface
from event queue. With this change the wait queue is not used anymore.
Remove it and 'wait_done' variable.

Signed-off-by: Amit Cohen <amcohen@nvidia.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://lore.kernel.org/r/f3af6a5a9dabd97d2920cefe475c6aa57767f504.1712062203.git.petrm@nvidia.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>