Add nucleo-f411re for testing STM32F411.
Fix registers.h to include F411 specific features.
TEST=Check uart,gpio works. Check BMI160 accel/gyro sensor works over
i2c
Install firmware with "make BOARD=nucleo-f411re flash"
BUG=b:38018926
BRANCH=none
Change-Id: I8514d1aa48e06708053e72f8d4be15738eda6cf4
Signed-off-by: Gwendal Grignou <gwendal@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/249994
Reviewed-by: Alexandru M Stan <amstan@chromium.org>