MIPS: RB532: replace raw volatile read with a readl

This patch replaces a raw read using volatiles
with a readl.

Signed-off-by: Florian Fainelli <florian@openwrt.org>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
diff --git a/arch/mips/rb532/gpio.c b/arch/mips/rb532/gpio.c
index 11d7127..b028779 100644
--- a/arch/mips/rb532/gpio.c
+++ b/arch/mips/rb532/gpio.c
@@ -70,7 +70,7 @@
 
 	spin_lock_irqsave(&dev3.lock, flags);
 
-	data = *(volatile unsigned *) (IDT434_REG_BASE + reg_offs);
+	data = readl(IDT434_REG_BASE + reg_offs);
 	for (i = 0; i != len; ++i) {
 		if (val & (1 << i))
 			data |= (1 << (i + bit));