arch/riscv: fix IRQ_SOFT for non-SMP

This fixes the software interrupt number for non-SMP cases

Signed-off-by: Yanfeng Liu <[email protected]>

arch/risc-v/src/common/riscv_exception.c

@@ -304,6 +304,6 @@ void riscv_exception_attach(void)
 #ifdef CONFIG_SMP
   irq_attach(RISCV_IRQ_SOFT, riscv_pause_handler, NULL);
 #else
-  irq_attach(RISCV_IRQ_MSOFT, riscv_exception, NULL);
+  irq_attach(RISCV_IRQ_SOFT, riscv_exception, NULL);
 #endif
 }