usb: gadget: f_ncm/u_ether: Move 'SKB reserve' quirk setup to u_ether

That quirk is required to make USB Ethernet gadget working on HW that
can't cope with unaligned DMA. For some reason only f_ncm sets up that
quirk, let's setup it directly in u_ether so other network models would
have that quirk applied as well. All network models have been tested with
ChipIdea UDC driver on NVIDIA Tegra20 SoC that require DMA to be aligned.

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>