rpi: get rid of BCM2835_BOARD_REV_* macros

rpi: get rid of BCM2835_BOARD_REV_* macros

There are two numbering schemes for the RPi revision values; old and new
scheme. The values within each scheme overlap. Hence, it doesn't make
sense to have absolute/global names for the revision IDs. Get rid of the
names and just use the raw revision/type values to set up the array of
per-revision data.

This change makes most sense when coupled with the next change. However,
it's split out so that the mechanical cut/paste is separate from the
logic changes for easier review and problem bisection.

Signed-off-by: Stephen Warren <swarren@wwwdotorg.org>