The global sequence number is usually 5 times bigger that the local
sequence number, so make it bigger to keep nice references.

It also change the type of the channel field. In this way, we obtain a
256byte structure which is a nice number for the kfifo (power 2).

Make it also aligned to 8Byte (64bit architecture)
Signed-off-by: Federico Vaga <federico.vaga@cern.ch>