Nucleo-64 boards do not have X3 crystal by default, so HSE is clocked
from MCO output of ST-LINK, and CONFIG_CLOCK_STM32_HSE_BYPASS should be
enabled. STM32F0 HSE somehow magically works even without that, but
to do so is the right thing.
Signed-off-by: Ilya Tagunov <tagunil@gmail.com>