Only bulk-only transport is supported by the currennt codebase, so
ep_bInterval and recv_intr_ep are not really used. Remove them and all
related code. While at it remove flags and subclass as well since they
are not really used anywhere in the codebase.

Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>