staging: usbip: userspace: unified command line arguments

The command `usbip attach' uses --host for specifing
the remote host, while `usbip list' uses --remote.
This is confusing and this patch adapts this.
In Addition changed the manpage and README accordingly.

Before:
 $ usbip attach --host <host> -b <busid>
 $ usbip list --remote <host>

Now:
 $ usbip attach --remote <host> -b <busid>
 $ usbip list --remote <host>

Signed-off-by: Kurt Kanzenbach <ly80toro@cip.cs.fau.de>
Signed-off-by: Stefan Reif <ke42caxa@cip.cs.fau.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>