fastboot: lift restrictions on !NET_LWIP for USB

fastboot: lift restrictions on !NET_LWIP for USB

Fastboot works either over TCP, UDP or USB. The latter doesn't have
anything to do with networking, thus should work just fine with
regardless which network stack is selected. In practice, header symbols
are used inside common code paths. Add some ifdeffery to guard against
that.

This will make fastboot over USB work with the new LWIP stack.

Signed-off-by: Michael Walle <mwalle@kernel.org>
Reviewed-by: Jerome Forissier <jerome.forissier@linaro.org>
Reviewed-by: Mattijs Korpershoek <mkorpershoek@baylibre.com>
Link: https://lore.kernel.org/r/20250312073655.2281377-1-mwalle@kernel.org
Signed-off-by: Mattijs Korpershoek <mkorpershoek@kernel.org>