libcpu/nuclei: Fix wrong RT_KERNEL_INTERRUPT_LEVEL
RT_KERNEL_INTERRUPT_LEVEL set to 0 is the lowest level.
#define SYSTICK_TICK_CONST (SOC_TIMER_FREQ / RT_TICK_PER_SECOND)
/* Interrupt level for kernel systimer interrupt and software timer interrupt */
-#define RT_KERNEL_INTERRUPT_LEVEL 1
+#define RT_KERNEL_INTERRUPT_LEVEL 0
/* Initial CSR MSTATUS value when thread created */
#define RT_INITIAL_MSTATUS (MSTATUS_MPP | MSTATUS_MPIE | MSTATUS_FS_INITIAL)
