arm: beetle: Fix UART1 IRQ number
arm: beetle: Fix UART1 IRQ number

The commit de78ecd "arm: beetle: Use device tree for IRQs" introduces
a regression related to UART1 IRQ.

On arm beetle the UART1 has IRQ number 2.

This patch restores the functionality modifying the arm beetle device
tree file.

Signed-off-by: Vincenzo Frascino <3ace7bb34570a19a202c4c73ce7a798ea734bba6@linaro.org>

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