netdevsim: drop code duplicated by a merge

Looks like the port adding loop makes a re-appearance on net-next
after net was merged back into it (even though it doesn't feature
in the merge diff).

The ports are already added in nsim_dev_create() so when we try
to add them again get EEXIST, and see:

netdevsim: probe of netdevsim0 failed with error -17

in the logs. When we remove the loop again the nsim_dev_probe()
and nsim_dev_remove() become a wrapper of nsim_dev_create() and
nsim_dev_destroy(). Remove this layer of indirection.

Fixes: d31e9558

 ("Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net")
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>