rdma: make RES_PID and RES_KERN_NAME alternative to each other

rdma: make RES_PID and RES_KERN_NAME alternative to each other

RDMA_NLDEV_ATTR_RES_PID and RDMA_NLDEV_ATTR_RES_KERN_NAME cannot be set
together, as evident for the fill_res_name_pid() function in the kernel
infiniband driver. This commit makes this clear at first glance, using
an else branch for the RDMA_NLDEV_ATTR_RES_KERN_NAME case.

This also helps coverity to better understand this code and avoid
producing a bogus warning complaining about mnl_attr_get_str overwriting
comme, and thus leaking the storage that comm points to.

Signed-off-by: Andrea Claudi <aclaudi@redhat.com>
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>