USB: UDC: net2280: Remove redundant "if" condition

The net2280 driver includes an unnecessary test for an endpoint's
queue being empty.  The test is redundant; it sits inside a
conditional block of an "if" statement which already tests the
endpoint's queue.

This patch removes the redundant test.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>