dts: stm32: Define stm32l073 as stm32l072 superset

STM32L073 soc variant is a STM32L072 with LCD peripheral.
Reflect this in dts definition by including stm32l072.dtsi
in stm32l073.dtsi.
This also allows to fix an issue on stm32l073 gpioe which
declared wrong reg definition.


Signed-off-by: Erwan Gouriou <erwan.gouriou@linaro.org>