USB: empeg: reimplement using generic framework

Kill custom read and write implementations (static 16*4k write-urb pool
shared among all ports in system).

Also remove old changelog entries in header (code is now gone, and
these entries can still be retrieved through git).

Compile-only tested.

Signed-off-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>