RDMA/efa: Fix success return value in case of error

Existing code would mistakenly return success in case of error instead
of a proper return value.

Fixes: e9c6c537

 ("RDMA/efa: Add common command handlers")
Reviewed-by: Firas JahJah <firasj@amazon.com>
Reviewed-by: Yossi Leybovich <sleybo@amazon.com>
Signed-off-by: Gal Pressman <galpress@amazon.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>