ARM: 7064/1: vexpress: Use wfi macro in platform_do_lowpower.

Current Versatile Express CPU hotplug code includes a hardcoded WFI
instruction, in ARM encoding.  When the kernel is compiled in Thumb-2
mode, this is invalid and causes the machine to hang hard when a CPU
is offlined.

Using the wfi macro (which uses the appropriate assembler mnemonic)
causes the correct instruction to be emitted in either case.  As a
consequence of this change, an apparently vestigial "cc" clobber is
dropped from the asm (the macro uses "memory" only).
Signed-off-by: NNick Bowler <nbowler@elliptictech.com>
Reviewed-by: NJamie Iles <jamie@jamieiles.com>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

arch/arm/mach-vexpress/hotplug.c

@@ -13,6 +13,7 @@
 #include <linux/smp.h>
 
 #include <asm/cacheflush.h>
+#include <asm/system.h>
 
 extern volatile int pen_release;
 
@@ -62,13 +63,7 @@ static inline void platform_do_lowpower(unsigned int cpu, int *spurious)
 	 * code will have already disabled interrupts
 	 */
 	for (;;) {
-		/*
-		 * here's the WFI
-		 */
-		asm(".word	0xe320f003\n"
-		    :
-		    :
-		    : "memory", "cc");
+		wfi();
 
 		if (pen_release == cpu) {
 			/*