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 <andre.przywara@arm.com>
Cc: Jagan Teki <jagan@amarulasolutions.com>
Cc: Phil Sutter <phil@nwl.cc>
Cc: Stefan Bosch <stefan_b@posteo.net>
Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/board/nokia/rx51/rx51.c b/board/nokia/rx51/rx51.c
index fd3cec8..99ca36f 100644
--- a/board/nokia/rx51/rx51.c
+++ b/board/nokia/rx51/rx51.c
@@ -241,6 +241,7 @@
 	return 0;
 }
 
+#ifdef CONFIG_REVISION_TAG
 /*
  * Routine: get_board_revision
  * Description: Return board revision.
@@ -249,6 +250,7 @@
 {
 	return simple_strtol(hw_build_ptr, NULL, 16);
 }
+#endif
 
 /*
  * Routine: setup_board_tags