logging: Make it possible to print category/subsys and timestamps

We want to see from which category/subsystem a certain log message
is coming from and use a different timestamp format as well. Add
two new bitfields. This doesn't change the size of the structure
and on 32bit we still have 27bits left.

The extended timestamp will take preference over the current and
default timestamp format.

Fixes: SYS#602
3 files changed