alpha: remove LCA and APECS based machines

alpha: remove LCA and APECS based machines

APECS is the DECchip 21071x chipset for the EV4 and EV45 generation, while
LCA is the integrated I/O support on the corresponding low-cost alpha
machines of that generation.

All of these CPUs lack the BWX extension for byte and word access, so
drop the chipset support and all associated machines.

Acked-by: Paul E. McKenney <paulmck@kernel.org>
Acked-by: Matt Turner <mattst88@gmail.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>