Clean cache_l1 and cache_l2 maintenance

L1 cache maintenance is using Virtual Memory, whereas cache L2 maintenance
uses Physical Memory

Signed-off-by: Pascal Brand <pascal.brand@st.com>
Reviewed-by: Jens Wiklander <jens.wiklander@linaro.org>
Tested-by: Pascal Brand <pascal.brand@linaro.org> (STM platform)