iwlagn: add IRQ tracing

The legacy IRQs could be read from a trace by their
IO accesses, but reading the ICT doesn't leave any
trace (pun intended ;-) ) so in order to see what
input they get we need to add specific tracepoints.

While at it, fix whitespace in two related places.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>