Allow vendor-init-actionable for ro.board.platform and sys.boot_from_charger_mode

ro.board.platform and sys.boot_from_charger_mode are already
public-readable, but they should be used as action triggers as well for
some products including Android Go devices.

Bug: 75987246
Test: succeeded building and tested with taimen
Change-Id: I140a8f7ef3fa9823ceced94b00a413800518c240
Merged-In: I140a8f7ef3fa9823ceced94b00a413800518c240
(cherry picked from commit 1f90ccef)