USB: u_ether: Configure the endpoints before enabling them in eth_stop()

The endpoints fail to enable if they are not configured. Hence configure
the IN and OUT endpoints in eth_stop() function before enabling them.

Change-Id: I936c5c492054cbc16bde6f1d0414712d8a0048d7
Signed-off-by: Rajkumar Raghupathy <raghup@codeaurora.org>