RISC-V: simplify software interrupt / IPI code

Rename handle_ipi to riscv_software_interrupt, drop the unused return
value and move the prototype to irq.h together with riscv_timer_interupt.
This allows simplifying the upcoming interrupt handling support.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>

arch/riscv/include/asm/irq.h

@@ -22,6 +22,7 @@
 #define INTERRUPT_CAUSE_EXTERNAL    9
 
 void riscv_timer_interrupt(void);
+void riscv_software_interrupt(void);
 
 #include <asm-generic/irq.h>
 

arch/riscv/include/asm/smp.h

@@ -44,9 +44,6 @@ void arch_send_call_function_single_ipi(int cpu);
  */
 #define raw_smp_processor_id() (*((int*)((char*)get_current() + TASK_TI_CPU)))
 
-/* Interprocessor interrupt handler */
-irqreturn_t handle_ipi(void);
-
 #endif /* CONFIG_SMP */
 
 #endif /* _ASM_RISCV_SMP_H */