ANDROID: db845c_gki.fragment: Remove CONFIG_USB_NET_AX8817X from fragment

After commit 20510ca6 ("ANDROID: gki - CONFIG_USB_NET_AX8817X=y")
the change in our fragment to enable CONFIG_USB_NET_AX8817X=m seems to
cause enough trouble to prevent us from booting (fails in early boot
before serial output).

After bisecting the cause down, I found removing our entry in the
fragment avoids the problem while keeping the onboard eth port
working.

Fixes: 20510ca6 ("ANDROID: gki - CONFIG_USB_NET_AX8817X=y")
Signed-off-by: John Stultz <john.stultz@linaro.org>
Change-Id: Idc72224aae26cdb15e877385bf9b16d534f77e8d