drivers: serial: Adapt gecko uart driver for Silabs EFM32HG
drivers: serial: Adapt gecko uart driver for Silabs EFM32HG

Happy Gecko has 2 USART not UART and also supports more pin locations.

Signed-off-by: Marcio Montenegro <e9732f5edd1736e87920cff7667ecfb0b77932fb@gmail.com>
Signed-off-by: Christian Taedcke <1d7d3458c4d94e1013a9872dbd5fe0865ba6a124@taedcke.com>

ldts/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,GiulianoFranchetto/zephyr,nashif/zephyr,explora26/zephyr,Vudentz/zephyr,ldts/zephyr,punitvara/zephyr,finikorg/zephyr,galak/zephyr,ldts/zephyr,punitvara/zephyr,GiulianoFranchetto/zephyr,ldts/zephyr,galak/zephyr,finikorg/zephyr,Vudentz/zephyr,nashif/zephyr,nashif/zephyr,GiulianoFranchetto/zephyr,Vudentz/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,punitvara/zephyr,ldts/zephyr,finikorg/zephyr,GiulianoFranchetto/zephyr,explora26/zephyr,explora26/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr,punitvara/zephyr,GiulianoFranchetto/zephyr,nashif/zephyr,explora26/zephyr,zephyrproject-rtos/zephyr,explora26/zephyr,punitvara/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,galak/zephyr,finikorg/zephyr,finikorg/zephyr