net: fix typo in drivers/net/usb/Kconfig

Replace invisible character with a space.

The diff looks like this on my terminal:
-        <A0>Choose this option if you're using a host-to-host cable
-        <A0>with one of these chips.
+         Choose this option if you're using a host-to-host cable
+         with one of these chips.

Reported by: Massimo Maiurana <maiurana@gmail.com>

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Cc: Massimo Maiurana <maiurana@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>