usb: hub: make minimum power-on delay configurable

This patch makes the minimum power-on delay for USB HUB
become configurable. The original design waits at least
100 msec here, but some EHCI controlers(e.g. Faraday EHCI)
are known to require much longer delay interval.

Signed-off-by: Kuo-Jung Su <dantesu@faraday-tech.com>
CC: Marek Vasut <marex@denx.de>
diff --git a/common/usb_hub.c b/common/usb_hub.c
index 0d79ec3..fc3a8c17 100644
--- a/common/usb_hub.c
+++ b/common/usb_hub.c
@@ -53,6 +53,10 @@
 #include <asm/4xx_pci.h>
 #endif
 
+#ifndef CONFIG_USB_HUB_MIN_POWER_ON_DELAY
+#define CONFIG_USB_HUB_MIN_POWER_ON_DELAY	100
+#endif
+
 #define USB_BUFSIZ	512
 
 static struct usb_hub_device hub_dev[USB_MAX_HUB];
@@ -148,8 +152,8 @@
 		debug("port %d returns %lX\n", i + 1, dev->status);
 	}
 
-	/* Wait at least 100 msec for power to become stable */
-	mdelay(max(pgood_delay, (unsigned)100));
+	/* Wait for power to become stable */
+	mdelay(max(pgood_delay, CONFIG_USB_HUB_MIN_POWER_ON_DELAY));
 }
 
 void usb_hub_reset(void)