ARM: at91: implement the standby function for pm/cpuidle

This patch groups the self-refresh on/cpu_do_idle/self-refresh off into
a single 'standby' function.

The standby routine for rm9200 has been turned into an asm routine to have
a better control of the self refresh and to prevent a memory access when
running this code.

Draining the write buffer is done automatically when switching for the self
refresh on sam9, so the instruction is added to the rm9200 only.

Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
diff --git a/arch/arm/mach-at91/pm.c b/arch/arm/mach-at91/pm.c
index d7e8d4c..d554e67 100644
--- a/arch/arm/mach-at91/pm.c
+++ b/arch/arm/mach-at91/pm.c
@@ -198,7 +198,6 @@
 
 static int at91_pm_enter(suspend_state_t state)
 {
-	u32 saved_lpr;
 	at91_gpio_suspend();
 	at91_irq_suspend();
 
@@ -254,16 +253,7 @@
 			 * For ARM 926 based chips, this requirement is weaker
 			 * as at91sam9 can access a RAM in self-refresh mode.
 			 */
-			asm volatile (	"mov r0, #0\n\t"
-					"b 1f\n\t"
-					".align 5\n\t"
-					"1: mcr p15, 0, r0, c7, c10, 4\n\t"
-					: /* no output */
-					: /* no input */
-					: "r0");
-			saved_lpr = sdram_selfrefresh_enable();
-			cpu_do_idle();
-			sdram_selfrefresh_disable(saved_lpr);
+			at91_standby();
 			break;
 
 		case PM_SUSPEND_ON: