fix failing RTC initialization for MTS_DRAGONFLY_F411RE#3573

Merged

0xc0170 merged 1 commit intoARMmbed:masterfrom

MultiTechSystems:dragonfly-rtc-fix

Jan 16, 2017

Commits on Jan 12, 2017

[MTS_DRAGONFLY_F411RE] use LSI for RTC since LSE is no longer populated by default
mfiore02
committed