soc: sam4l: Add US_MR_CHRL_{n}_BIT Register Aliases for SAM4L Chips
soc: sam4l: Add US_MR_CHRL_{n}_BIT Register Aliases for SAM4L Chips

Required for building the new usart driver with runtime configuration
support on all supported sam platforms.

Signed-off-by: Nick Kraus <75ef9faee755c70589550b513ad881e5a603182c@nckraus.com>

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