xhci: Don't warn about zeroed bMaxBurst descriptor field.

The USB 3.0 specification says that the bMaxBurst field in the SuperSpeed
Endpoint Companion descriptor is supposed to indicate how many packets a
SS device can handle before it needs to wait for an explicit handshake
from the host controller.  A zero value means the device can only handle
one packet before it needs a handshake.  Remove a warning in the xHCI
driver that implies this is an invalid value.
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>

drivers/usb/host/xhci-mem.c

@@ -1215,8 +1215,6 @@ int xhci_endpoint_init(struct xhci_hcd *xhci,
 		ep_ctx->ep_info2 |= cpu_to_le32(MAX_PACKET(max_packet));
 		/* dig out max burst from ep companion desc */
 		max_packet = ep->ss_ep_comp.bMaxBurst;
-		if (!max_packet)
-			xhci_warn(xhci, "WARN no SS endpoint bMaxBurst\n");
 		ep_ctx->ep_info2 |= cpu_to_le32(MAX_BURST(max_packet));
 		break;
 	case USB_SPEED_HIGH: