m32r: Exit ei_handler directly for no IRQ case or IPI operations

If no IRQ request is found in the IRQ check of ei_handler,
we can exit directly by jumping "restore_all", instead of via
"ret_from_intr".

This modification is also likely effective for IPI operations,
because scheduler call never happen at the exit of IPIs.

Signed-off-by: Hitoshi Yamamoto <[e-mail]>
Signed-off-by: Hirokazu Takata <[e-mail]>

arch/m32r/kernel/entry.S

···
 	.fillinsn
 1:
 	addi	sp, #4
-	bra	ret_to_intr
+	bra	restore_all
 	.fillinsn
 2:
 	srli	r0, #2
···
 	pop	r14
 	seth	r0, #shigh(M32R_ICU_IMASK_ADDR)
 	st	r14, @(low(M32R_ICU_IMASK_ADDR),r0)
-ret_to_intr:
 	bra  ret_from_intr
 
 /*