soc: xtensa: intel_adsp: fix build error for cavs

Build of Intel cAVS2.5 platforms fails due to undefined reference
sys_cache_data_flush_and_invd_all(). Fix this by adding missing
header include to bring in the inline definition for this function.

Fixes: 6388f5f1 ("xtensa: use sys_cache API instead of custom interfaces")
Signed-off-by: Kai Vehmanen <kai.vehmanen@linux.intel.com>