arch/Config.in: remove BR2_ARCH_HAS_MMU_MANDATORY from BR2_aarch64*

arch/Config.in: remove BR2_ARCH_HAS_MMU_MANDATORY from BR2_aarch64*

Selecting BR2_ARCH_HAS_MMU_MANDATORY from BR2_aarch64 and
BR2_aarch64_be doesn't make much sense, because the actual ARM cores
described in arch/Config.in.arm then all select
BR2_ARCH_HAS_MMU_OPTIONAL. So we end up with both
BR2_ARCH_HAS_MMU_OPTIONAL and BR2_ARCH_HAS_MMU_MANDATORY, which
doesn't make any sense.

To prevent this, we remove the selection of BR2_ARCH_HAS_MMU_MANDATORY
from BR2_aarch64 and BR2_aarch64_be, and let arch/Config.in.arm do its
job. What arch/Config.in.arm does is currently incorrect, but it will
be fixed in a separate commit.

Signed-off-by: Thomas Petazzoni <[email protected]>
Signed-off-by: Yann E. MORIN <[email protected]>