usb: fix uninitialized variable warning in keyspan_pda

This fixes the compiler warning.

Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/usb/serial/keyspan_pda.c b/drivers/usb/serial/keyspan_pda.c
index 644a1ea..60b3e22 100644
--- a/drivers/usb/serial/keyspan_pda.c
+++ b/drivers/usb/serial/keyspan_pda.c
@@ -408,7 +408,7 @@
 			     3, /* get pins */
 			     USB_TYPE_VENDOR|USB_RECIP_INTERFACE|USB_DIR_IN,
 			     0, 0, &data, 1, 2000);
-	if (rc > 0)
+	if (rc >= 0)
 		*value = data;
 	return rc;
 }