Squashed commit of the following:
arch/arm/src/stm32f0l0: Various changes for a clean compilation. Still does not compile correctly due to missing FLASH latency definitions.
arch/arm/src/stm32f0l0/hardware: Add framework for the STM32 L0. Currently set to same as the STM32F0.
arch/arm/src/stm32f0l0/hardware: Very fragmentary FLASH header register definitions for the STM32 L0.
arch/arm/src/stm32f0l0: Bring in DMA v1. Cannot possibly be functionaly yet due to the limited number for M0 interrupts.
arch/arm/src/stm32f0l0: Add STM32 F0/L0 LSE and backup power domain controls.
arch/arm/src/stm32f0l0/hardware/stm32l0_pwr.h: Add STM32L0 PWR header file.
arch/arm/include/stm32f0l0/chip.h: Clean up WIP chip header file.
arch/arm/include/stm32f0l0/chip.h: WIP.
arm/src/stm32f0l0: Resolve some small differences between F0 and L0 GPIO pin options.
arch/arm/src/stm32f0l0: Better integrate STM32L0 header files.
nuttx/arch/arm/include/stm32f0l0: Add STM32L0 IRQ number definition file.
arch/arm/src/stm32f0l0: Add STM32L0 RCC driver.
arch/arm/src/stm32f0l0/hardware: Adds basic STM32L0 header files.
arch/arm/src/stm32f0l0: Add STM32L0 chip selections.
configs/: Hook new STM32L0 boards into the configuration system.
configs: nucleo boards use as default ST LINK MCO as clock input from MCU and for this HSEBYP must be enabled
configs: add basic support for nucleo-l073rz
configs: add basic support for b-l072z-lrwan1
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