chip/stm32: Fix compile with gcc8
chip/stm32: Fix compile with gcc8

gcc8 packs uint8 arrays more tightly sometimes, which is bad if a
device expects a certain alignment, so make the 4byte alignment of
gcc 4.9 explicit for the buffers.

BUG=b:132204142
TEST=sweetberry firmware built with coreboot-sdk reaches the console

Change-Id: I24cf151d2df21e106fbb7e8f5b16a3bab81b09ab
Signed-off-by: Patrick Georgi <bc411205f21846a74924ee7b489c75617ec76078@google.com>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/1899437
Tested-by: Patrick Georgi <bc411205f21846a74924ee7b489c75617ec76078@chromium.org>
Commit-Queue: Patrick Georgi <bc411205f21846a74924ee7b489c75617ec76078@chromium.org>
Reviewed-by: Brian Nemec <4bb9322d2721abaa797f20e8e3863e6a19240e0a@chromium.org>
Reviewed-by: Patrick Georgi <bc411205f21846a74924ee7b489c75617ec76078@chromium.org>

coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec