ARM: highbank: use wfi macro instead of inline asm

Older compilers don't recognize v7 wfi instruction, so use wfi macro to
fix builds on old compilers.

Signed-off-by: Rob Herring <rob.herring@calxeda.com>

board/highbank/highbank.c

@@ -88,5 +88,6 @@ void dram_init_banksize(void)
 void reset_cpu(ulong addr)
 {
 	writel(HB_PWR_HARD_RESET, HB_SREG_A9_PWR_REQ);
-	asm("	wfi");
+
+	wfi();
 }