net: core: dev_get_valid_name is now the same as dev_alloc_name_ns

If name contains a %, it's easy to see that this patch doesn't change
anything (other than eliminate the duplicate dev_valid_name
call). Otherwise, we'll now just spend a little time in snprintf()
copying name to the stack buffer allocated in dev_alloc_name_ns, and do
the __dev_get_by_name using that buffer rather than name.

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: David S. Miller <davem@davemloft.net>