chip/stm32: Fix bug that LPTIM_PERIOD_US became unsigned long.
chip/stm32: Fix bug that LPTIM_PERIOD_US became unsigned long.

Due to a refactoring of bit shifts (BIT macro), LPTIM_PERIOD_US changed
from int to unsigned int, which in turn changed behavior of
set_lptim_event. This causes a watchdog reset during a long suspend. In
particular, this caused the stm32h7 FPMCU to reboot during long suspend
and fingerprint unlock to not work.

BUG=b:140538084
BRANCH=none
TEST=verified that FPMCU no longer reboots during deep sleep, fingerprint
	unlock works after deep sleeping for a whole night.

Change-Id: If2ed9cb94aad4216012e28ffec530bc4ce858093
Signed-off-by: Yicheng Li <77a205905d8955597c069555e9569c30512f6bd8@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/1854785
Reviewed-by: Nicolas Norvez <3001a977f47a2bc94ec05551872e2ce88b323556@chromium.org>

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