STM32F: Remove support for this family

There are no boards left that use this family of STM32 parts.  If we
add one later we can resurect support.

Signed-off-by: Anton Staaf <robotboy@chromium.org>

BRANCH=None
BUG=None
TEST=make buildall -j

Change-Id: If985a9e9f93c935e98c93f33c075ce00cb9a91ac
Reviewed-on: https://chromium-review.googlesource.com/282532
Tested-by: Anton Staaf <robotboy@chromium.org>
Reviewed-by: Randall Spangler <rspangler@chromium.org>
Commit-Queue: Anton Staaf <robotboy@chromium.org>
Trybot-Ready: Anton Staaf <robotboy@chromium.org>
21 files changed