net/appletalk: Supply missing net/Space.h include file

If the header file containing a function's prototype isn't included by
the sourcefile containing the associated function, the build system
complains of missing prototypes.

Fixes the following W=1 kernel build warning(s):

drivers/net/appletalk/cops.c:213:28: warning: no previous prototype for ‘cops_probe’ [-Wmissing-prototypes]
drivers/net/appletalk/ltpc.c:1014:28: warning: no previous prototype for ‘ltpc_probe’ [-Wmissing-prototypes]

Signed-off-by: Wang Hai <wanghai38@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>