MPS2_AN500 have UART1,2,3,4, TIMER0,1, is a great board to do irqprio test. enable CONFIG_ARCH_IRQPRIO, and use 'qemu-system-arm -M mps2-an500 -nographic -kernel nuttx.bin' to lauch qemu Signed-off-by: buxiasen <buxiasen@xiaomi.com>