The AArch64 cache implementation does not define
rtems_cache_disable_data(), but declares that it does via
CPU_CACHE_SUPPORT_PROVIDES_DISABLE_DATA. The existing implementation of
_CPU_cache_disable_data() is sufficient to enable this functionality
without the erroneous cache feature flag.
Closes#4569
This fixes a bug where addresses were not being aligned correctly.
Addresses used in cache functions are now aligned consistently using
RTEMS_ALIGN_DOWN.
