powerpc/83xx: Do not configure or probe disabled FSL DR USB controllers

On MPC837X CPUs Dual-Role USB isn't always available (for example DR
USB pins can be muxed away to eSDHC).

U-Boot adds status = "disabled" property into the DR USB nodes to
indicate that we must not try to configure or probe Dual-Role USB,
otherwise we'll break eSDHC support on targets with MPC837X CPUs.

Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
diff --git a/arch/powerpc/sysdev/fsl_soc.c b/arch/powerpc/sysdev/fsl_soc.c
index 115cb16..a01c89d 100644
--- a/arch/powerpc/sysdev/fsl_soc.c
+++ b/arch/powerpc/sysdev/fsl_soc.c
@@ -22,6 +22,7 @@
 #include <linux/module.h>
 #include <linux/device.h>
 #include <linux/platform_device.h>
+#include <linux/of.h>
 #include <linux/of_platform.h>
 #include <linux/phy.h>
 #include <linux/phy_fixed.h>
@@ -328,6 +329,9 @@
 		struct fsl_usb2_platform_data usb_data;
 		const unsigned char *prop = NULL;
 
+		if (!of_device_is_available(np))
+			continue;
+
 		memset(&r, 0, sizeof(r));
 		memset(&usb_data, 0, sizeof(usb_data));