powerpc: Use the same interrupt prolog for perfmon as other interrupts

The perfmon interrupt is the sole user of a special variant of the
interrupt prolog which differs from the one used by external and timer
interrupts in that it saves the non-volatile GPRs and doesn't turn the
runlatch on.

The former is unnecessary and the later is arguably incorrect, so
let's clean that up by using the same prolog. While at it we rename
that prolog to use the _ASYNC prefix.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/include/asm/exception-64s.h

@@ -297,21 +297,10 @@ label##_common:						\
 
 /*
  * Like STD_EXCEPTION_COMMON, but for exceptions that can occur
- * in the idle task and therefore need the special idle handling.
+ * in the idle task and therefore need the special idle handling
+ * (finish nap and runlatch)
  */
-#define STD_EXCEPTION_COMMON_IDLE(trap, label, hdlr)	\
-	.align	7;					\
-	.globl label##_common;				\
-label##_common:						\
-	EXCEPTION_PROLOG_COMMON(trap, PACA_EXGEN);	\
-	FINISH_NAP;					\
-	DISABLE_INTS;					\
-	bl	.save_nvgprs;				\
-	addi	r3,r1,STACK_FRAME_OVERHEAD;		\
-	bl	hdlr;					\
-	b	.ret_from_except
-
-#define STD_EXCEPTION_COMMON_LITE(trap, label, hdlr)	\
+#define STD_EXCEPTION_COMMON_ASYNC(trap, label, hdlr)	\
 	.align	7;					\
 	.globl label##_common;				\
 label##_common:						\

arch/powerpc/kernel/exceptions-64s.S

@@ -458,15 +458,15 @@ machine_check_common:
 	bl	.machine_check_exception
 	b	.ret_from_except
 
-	STD_EXCEPTION_COMMON_LITE(0x500, hardware_interrupt, do_IRQ)
-	STD_EXCEPTION_COMMON_LITE(0x900, decrementer, .timer_interrupt)
+	STD_EXCEPTION_COMMON_ASYNC(0x500, hardware_interrupt, do_IRQ)
+	STD_EXCEPTION_COMMON_ASYNC(0x900, decrementer, .timer_interrupt)
 	STD_EXCEPTION_COMMON(0xa00, trap_0a, .unknown_exception)
 	STD_EXCEPTION_COMMON(0xb00, trap_0b, .unknown_exception)
 	STD_EXCEPTION_COMMON(0xd00, single_step, .single_step_exception)
 	STD_EXCEPTION_COMMON(0xe00, trap_0e, .unknown_exception)
         STD_EXCEPTION_COMMON(0xe40, emulation_assist, .program_check_exception)
         STD_EXCEPTION_COMMON(0xe60, hmi_exception, .unknown_exception)
-	STD_EXCEPTION_COMMON_IDLE(0xf00, performance_monitor, .performance_monitor_exception)
+	STD_EXCEPTION_COMMON_ASYNC(0xf00, performance_monitor, .performance_monitor_exception)
 	STD_EXCEPTION_COMMON(0x1300, instruction_breakpoint, .instruction_breakpoint_exception)
 #ifdef CONFIG_ALTIVEC
 	STD_EXCEPTION_COMMON(0x1700, altivec_assist, .altivec_assist_exception)