[PATCH] USB dummy_hcd: Centralize link state computations

This patch adds to the dummy_hcd driver a new routine for keeping track of
all changes in the state of the emulated USB link.  The logic is now kept
in one spot instead of spread around, and it's easier to verify and
update the code.  The behavior of the port features has been corrected in
a few respects as well (for instance, if the POWER feature is clear then
none of the other features can be set).

Also added is support for the (relatively new) _connect() and
_disconnect() calls of the Gadget API.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>