stm32cube: Update build system to support stm32f7xx

Get stm32f7xx support ready in build system.
Provide minimal file inclusion to support stm32f7 based board
port.

Change-Id: Idf949ef4a627bbd82e7bf95a9ae1d3d073654115
Signed-off-by: Erwan Gouriou <erwan.gouriou@linaro.org>
2 files changed