stm32cube: Update build system to support stm32f2xx Get stm32f2xx support ready in build system. Provide minimal file inclusion to support stm32f2 based board port. Change-Id: Ice1231709e778e00a51a395decb3447fc58c0bbf Signed-off-by: Erwan Gouriou <erwan.gouriou@linaro.org>