stm32: unimplemented hibernate hard-reboots instead of hanging
stm32: unimplemented hibernate hard-reboots instead of hanging

This more closely emulates what LM4 does if it hibernates and then
immediately wakes.  Keeps the system from becoming silently
unresponsive if a hibernate is triggered on STM32.

BUG=chrome-os-partner:18371
BRANCH=none
TEST=from ec console, 'hibernate' reboots instead of hanging

Change-Id: I031f79239725d69ba054323e4fbf8f59133f2093
Signed-off-by: Randall Spangler <62698fdbb84d1779579ee80c3f39fac22017e5bc@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/46286
Reviewed-by: Vic Yang <5fd92abeee651458f98e2856f4f200ee971cee4d@chromium.org>

coreboot/chrome-ec,coreboot/chrome-ec,gelraen/cros-ec,alterapraxisptyltd/chromium-ec,fourier49/BIZ_EC,mtk09422/chromiumos-platform-ec,eatbyte/chromium-ec,mtk09422/chromiumos-platform-ec,akappy7/ChromeOS_EC_LED_Diagnostics,thehobn/ec,alterapraxisptyltd/chromium-ec,coreboot/chrome-ec,fourier49/BIZ_EC,coreboot/chrome-ec,fourier49/BZ_DEV_EC,gelraen/cros-ec,akappy7/ChromeOS_EC_LED_Diagnostics,longsleep/ec,fourier49/BIZ_EC,md5555/ec,eatbyte/chromium-ec,akappy7/ChromeOS_EC_LED_Diagnostics,longsleep/ec,md5555/ec,alterapraxisptyltd/chromium-ec,gelraen/cros-ec,thehobn/ec,fourier49/BZ_DEV_EC,coreboot/chrome-ec,akappy7/ChromeOS_EC_LED_Diagnostics,coreboot/chrome-ec,eatbyte/chromium-ec,md5555/ec,md5555/ec,akappy7/ChromeOS_EC_LED_Diagnostics,longsleep/ec,longsleep/ec,fourier49/BIZ_EC,fourier49/BZ_DEV_EC,eatbyte/chromium-ec,gelraen/cros-ec,fourier49/BZ_DEV_EC,mtk09422/chromiumos-platform-ec,mtk09422/chromiumos-platform-ec,alterapraxisptyltd/chromium-ec,thehobn/ec,thehobn/ec