ARM: imx: use generic function to exit coherency

The common ARM architecture code provides a generic function to exit
coherency called v7_exit_coherency_flush(). Replace the machine
specific implementation using the generic function.

Tested on a i.MX 6Dual by hotplugging the secondary CPU under load
through sysfs several 1000 times.
Tested-by: Stefan Agner <stefan@agner.ch>
Signed-off-by: Stefan Agner <stefan@agner.ch>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm/mach-imx/hotplug.c

@@ -6,32 +6,12 @@
 
 #include <linux/errno.h>
 #include <linux/jiffies.h>
+#include <asm/cacheflush.h>
 #include <asm/cp15.h>
 #include <asm/proc-fns.h>
 
 #include "common.h"
 
-static inline void cpu_enter_lowpower(void)
-{
-	unsigned int v;
-
-	asm volatile(
-		"mcr	p15, 0, %1, c7, c5, 0\n"
-	"	mcr	p15, 0, %1, c7, c10, 4\n"
-	/*
-	 * Turn off coherency
-	 */
-	"	mrc	p15, 0, %0, c1, c0, 1\n"
-	"	bic	%0, %0, %3\n"
-	"	mcr	p15, 0, %0, c1, c0, 1\n"
-	"	mrc	p15, 0, %0, c1, c0, 0\n"
-	"	bic	%0, %0, %2\n"
-	"	mcr	p15, 0, %0, c1, c0, 0\n"
-	  : "=&r" (v)
-	  : "r" (0), "Ir" (CR_C), "Ir" (0x40)
-	  : "cc");
-}
-
 /*
  * platform-specific code to shutdown a CPU
  *
@@ -39,7 +19,7 @@ static inline void cpu_enter_lowpower(void)
  */
 void imx_cpu_die(unsigned int cpu)
 {
-	cpu_enter_lowpower();
+	v7_exit_coherency_flush(louis);
 	/*
 	 * We use the cpu jumping argument register to sync with
 	 * imx_cpu_kill() which is running on cpu0 and waiting for