staging: usbip: userspace: usbip_network: rename and cleanup function

Rename tcp_connection to usbip_net_tcp_connection, which alludes to a
usbip network library that will eventually follow. The implementation
of this function has also been cleaned up.

Headers had to be adjusted due to the elimination of the old usbip.h.

Signed-off-by: matt mooney <mfm@muteddisk.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>