boards: arm: st_stm32: add lptimer to the stm32l562e dk board

This patch introduces the support of the LowPower Timer
for the STM32l562ze disco kit (sec. and non-sec. version)
LSE clock is selected as LPTIM clock source on this board.

Signed-off-by: Francois Ramu <francois.ramu@st.com>
5 files changed