soc: arm: stm32f0: Add additional UARTs.
soc: arm: stm32f0: Add additional UARTs.

Add support for UARTs 3-6 to the stm32f030xc SoC. These additional UARTs
share a single interrupt line, so only one may be enabled at a time.

Signed-off-by: Brian Kubisiak <760e7dab2836853c63805033e514668301fa9c47@kubisiak.com>

nashif/zephyr,Vudentz/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,nashif/zephyr,Vudentz/zephyr,finikorg/zephyr,finikorg/zephyr,Vudentz/zephyr,nashif/zephyr,galak/zephyr,galak/zephyr,Vudentz/zephyr,finikorg/zephyr,nashif/zephyr,finikorg/zephyr,galak/zephyr,Vudentz/zephyr,finikorg/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr