IB/mlx4: In mlx4_ib_demux_cm, print out GUID in host-endian order

If a GUID is not found, the 64-bit GUID printed in the message log
warning should converted to host-endian order for printing.

Found by Doug Ledford and Hal Rosenstock. Fix suggested by Hal.

Signed-off-by: Hal Rosenstock <hal@dev.mellanox.co.il>
Signed-off-by: Jack Morgenstein <jackm@dev.mellanox.co.il>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>