stm32: Add header guard and fix fmt/doc of registers header file

We enforce that all family specific registers file can only be
included from registers.h.

We add a brief history and rationale behind splitting registers.h into
multiple family specific header files.

We fix formatting of preprocessor conditionals and documentation.

BRANCH=none
BUG=none
TEST=make buildall -j
TEST=Grab registers-extract.bash
     from http://go/bit/hesling/6385147721023488/4 .
     chmod +x ./registers-extract.bash
     ./registers-extract.bash board-regs-new
     git checkout cros/master
     ./registers-extract.bash board-regs-original
     diff board-regs-original board-regs-new
     [ $? -eq 0 ] && echo "# Good2Go" || echo "# Bad"

Signed-off-by: Craig Hesling <hesling@chromium.org>
Change-Id: I5d5983eb1e0cf7fb46339cba2987d551ff6b16cc
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/1693879
Reviewed-by: Daisuke Nojiri <dnojiri@chromium.org>

0 files changed, 0 insertions, 0 deletions