Disable Network file system support.

Reviewed-at: https://android-review.googlesource.com/#/c/409559/Signed-off-by: Roberto Pereira <rpere@google.com>
[AmitP: cherry-picked this change from Android common kernel
        and updated commit message]
Signed-off-by: Amit Pundir <amit.pundir@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>