decnet: Remove unnecessary check for dev->name

Clang warns that the address of a pointer will always evaluated as true
in a boolean context.

net/decnet/dn_dev.c:1366:10: warning: address of array 'dev->name' will
always evaluate to 'true' [-Wpointer-bool-conversion]
                                dev->name ? dev->name : "???",
                                ~~~~~^~~~ ~
1 warning generated.

Link: https://github.com/ClangBuiltLinux/linux/issues/116
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
Reviewed-by: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: David S. Miller <davem@davemloft.net>