arm: Disable ATAGs support

arm: Disable ATAGs support

With the exceptions of ds109, ds414, icnova-a20-swac, nokia_rx51 and
stemmy, disable ATAG support.  A large number of platforms had enabled
support but never supported a kernel so old as to require it.  Further,
some platforms are old enough to support both, but are well supported by
devicetree booting, and have been for a number of years.  This is
because some of the ATAGs related functions have been re-used to provide
the same kind of information, but for devicetree or just generally to
inform the user.  When needed still, rename these functions to
get_board_revision() instead, to avoid conflicts.  In other cases, these
functions were simply unused, so drop them.

Cc: Andre Przywara <[email protected]>
Cc: Jagan Teki <[email protected]>
Cc: Phil Sutter <[email protected]>
Cc: Stefan Bosch <[email protected]>
Signed-off-by: Tom Rini <[email protected]>