cavs: remove unused and dangerous definitions

uncache_to_cache(), cache_to_uncache() and is_uncached() macros
are currently unused in Zephyr, besides the former two are
dangerous because they add and subtract an offset instead of
masking and unmasking a bit, which can lead to wrong addresses
if applied repeatedly. Remove these macros for now, we can
re-add them later if needed in their fixed versions.

Signed-off-by: Guennadi Liakhovetski <guennadi.liakhovetski@linux.intel.com>