board: cssi: Use HAVE_VENDOR_COMMON_LIB logic

Instead of cross using cross-directory makefile directives,
add a Makefile in board/cssi/common/ directory in order to
benefit from HAVE_VENDOR_COMMON_LIB logic.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
3 files changed