sparc64: print debug messages when reading from LDC channel

Print debug messages when reading from given LDC channel.

Signed-off-by: Jagannathan Raman <jag.raman@oracle.com>
Reviewed-by: Aaron Young <aaron.young@oracle.com>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Reviewed-by: Bijan Mottahedeh <bijan.mottahedeh@oracle.com>
Reviewed-by: Liam Merwick <liam.merwick@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>