Kill custom read and write implementations (static per-port,
singleton(!) urb pool).

Also remove changelog header (can be retrieved through git).

Read processing and write-buffer handling tested using a cp210x device
in a loopback setup.
Signed-off-by: NJohan Hovold <jhovold@gmail.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>