cmake: board_check_revision() also accepts a list of valid revisions

[tejlmand]

To remove the need of empty config files, the board_check_revision()
now accepts a list of valid revisions.

As example:

board_check_revision(
  FORMAT MAJOR.MINOR.PATCH
  VALID_REVISIONS 0.1.0 0.5.0 0.10.0
)

The code is still compatible with the <board>_<revision>.conf changes
so that if different revisions of a board has Kconfig differences, then
there is no need to also specify the list of valid revisions.

Signed-off-by: Torsten Rasmussen Torsten.Rasmussen@nordicsemi.no

[mbolivar-nordic]

Looks good. Just to confirm, the point is to allow revisions that only have DT overlays, right?

That makes sense. In retrospect, hardware differences without software differences are probably more common. We probably should have looked for overlay files and made .conf fragments optional from the beginning instead.

Just a few documentation nits.

[tejlmand]

Looks good. Just to confirm, the point is to allow revisions that only have DT overlays, right?

Correct. Reviewing #31624 made me realize the empty files are not so nice.
Or in general not make assumptions on what is required to detect a revision.

That makes sense. In retrospect, hardware differences without software differences are probably more common. We probably should have looked for overlay files and made .conf fragments optional from the beginning instead.

You're probably right.