USB: "sparse" cleanups for usb gadgets

This removes complaints about the gadget stack which are generated by
the currrent "sparse":  it doesn't like the fact that zero is the null
pointer.  (Last I checked, C guarantees that's correct ...)

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/usb/gadget/zero.c b/drivers/usb/gadget/zero.c
index a2e6e3fc..fcfe869 100644
--- a/drivers/usb/gadget/zero.c
+++ b/drivers/usb/gadget/zero.c
@@ -653,7 +653,8 @@
 			result = usb_ep_enable (ep, d);
 			if (result == 0) {
 				ep->driver_data = dev;
-				if (source_sink_start_ep (ep, gfp_flags) != 0) {
+				if (source_sink_start_ep(ep, gfp_flags)
+						!= NULL) {
 					dev->in_ep = ep;
 					continue;
 				}
@@ -667,7 +668,8 @@
 			result = usb_ep_enable (ep, d);
 			if (result == 0) {
 				ep->driver_data = dev;
-				if (source_sink_start_ep (ep, gfp_flags) != 0) {
+				if (source_sink_start_ep(ep, gfp_flags)
+						!= NULL) {
 					dev->out_ep = ep;
 					continue;
 				}