ieee1394: add preprocessor constant for invalid csr address

ieee1394: add preprocessor constant for invalid csr address

Replace occurrences of the magic value ~(u64)0 for invalid
CSR address spaces by a named constant for better readability.

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
Signed-off-by: Ben Collins <bcollins@ubuntu.com>