Rename driver file to BSEC2.
Split header file in IP and feature parts.
Several corrections and improvements.

Change-Id: I1981536398d598d67a19d2d7766dacc18de72ec1
Signed-off-by: Nicolas Le Bayon <nicolas.le.bayon@st.com>
Signed-off-by: Yann Gautier <yann.gautier@st.com>