RDMA/irdma: Prevent some integer underflows

My static checker complains that:

    drivers/infiniband/hw/irdma/ctrl.c:3605 irdma_sc_ceq_init()
    warn: can subtract underflow 'info->dev->hmc_fpm_misc.max_ceqs'?

It appears that "info->dev->hmc_fpm_misc.max_ceqs" comes from the firmware
in irdma_sc_parse_fpm_query_buf() so, yes, there is a chance that it could
be zero.  Even if we trust the firmware, it's easy enough to change the
condition just as a hardenning measure.

Fixes: 3f49d684 ("RDMA/irdma: Implement HW Admin Queue OPs")
Link: https://lore.kernel.org/r/20220307125928.GE16710@kili


Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Shiraz Saleem <shiraz.saleem@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>