MIPS: Create a common <asm/mach-generic/war.h>

11 platforms require at least one of these workarounds to be enabled; 22
platforms do not.  In the latter case we can fall back to a generic version.

Note that this also deletes an orphaned reference to RM9000_CDEX_SMP_WAR.

Suggested-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Kevin Cernekee <cernekee@gmail.com>
Signed-off-by: Andrew Bresticker <abrestic@chromium.org>
Reviewed-by: James Hogan <james.hogan@imgtec.com>
Cc: devicetree@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-mips@linux-mips.org
Cc: Ezequiel Garcia <ezequiel.garcia@imgtec.com>
Cc: James Hartley <james.hartley@imgtec.com>
Cc: James Hogan <james.hogan@imgtec.com>
Patchwork: https://patchwork.linux-mips.org/patch/9567/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>