USB: musb: sysfs mode updates

Fix three omissions in the "mode" sysfs attribute support:
  (a) inability to report errors;
  (b) no DaVinci support ... just report an error;
  (c) for omap2430, accepting unsupportable values

The 2430 stuff is still odd....

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Felipe Balbi <felipe.balbi@nokia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/usb/musb/davinci.c b/drivers/usb/musb/davinci.c
index dfb3bcb..87aef82 100644
--- a/drivers/usb/musb/davinci.c
+++ b/drivers/usb/musb/davinci.c
@@ -364,6 +364,12 @@
 	return IRQ_HANDLED;
 }
 
+int musb_platform_set_mode(struct musb *musb, u8 mode)
+{
+	/* EVM can't do this (right?) */
+	return -EIO;
+}
+
 int __init musb_platform_init(struct musb *musb)
 {
 	void __iomem	*tibase = musb->ctrl_base;