ARM: imx6: mark OCRAM mapping read-only

iMX6 needs to write some code to OCRAM which resumes the DDR controller
after suspend. However, merely using __arm_ioremap_exec() causes the
kernel to complain of a W+X mapping. Solve this by using the newly
introduced __arm_iomem_set_ro() function to prevent inadvertent or
malicious writes to code we may later execute.
Tested-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>

arch/arm/mach-imx/pm-imx6.c

@@ -571,6 +571,8 @@ static int __init imx6q_suspend_init(const struct imx6_pm_socdata *socdata)
 		&imx6_suspend,
 		MX6Q_SUSPEND_OCRAM_SIZE - sizeof(*pm_info));
 
+	__arm_iomem_set_ro(suspend_ocram_base, MX6Q_SUSPEND_OCRAM_SIZE);
+
 	goto put_device;
 
 pl310_cache_map_failed: