Fix all the whitespace

- remove trailing whitespace
- remove duplicate blank lines
- remove blank lines at end of files

Fix licenses

sel4bench: improve interface

- define array of generic events
- drop generic events that don't exist for all platforms (i.e are not
generic)
- define number of generic events
- define types to illustate the difference between a counter and an
event

libsel4bench: Add performance counter descriptions for runtime display