usb: gadget: u_ether: Fix MTU size mismatch with RX packet size

usb: gadget: u_ether: Fix MTU size mismatch with RX packet size

commit 0a88fa221ce911c331bf700d2214c5b2f77414d3 upstream.

Fix the MTU size issue with RX packet size as the host sends the packet
with extra bytes containing ethernet header. This causes failure when
user sets the MTU size to the maximum i.e. 15412. In this case the
ethernet packet received will be of length 15412 plus the ethernet header
length. This patch fixes the issue where there is a check that RX packet
length must not be more than max packet length.

Fixes: bba787a860fa ("usb: gadget: ether: Allow jumbo frames")
Signed-off-by: Manish Narani <manish.narani@xilinx.com>
Cc: stable <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/1605597215-122027-1-git-send-email-manish.narani@xilinx.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>