boards: stm32f4: Extract common config options

Move common config options one level up to try to simplify the per-board
defconfig

Change-Id: I3d80fa494050634d0f877af2015b01b85df20d1d
Signed-off-by: Amit Kucheria <amit.kucheria@linaro.org>
Signed-off-by: Kumar Gala <kumar.gala@linaro.org>
3 files changed