Feature reports should only be sent on the control endpoint.

The USB HID standard is unclear and confusing on this issue. It seems to
suggest that Feature reports can be sent on a HID device's Interrupt OUT
endpoint.  This cannot be the case because the report type is not encoded in
transfers sent out the Interrput OUT endpoint.  If Feature reports were sent on
the Interrupt OUT endpint, they would be indistinguishable from Output reports
in the case where Report IDs were not used.

Further, Windows and Mac OS X do not send Feature reports out the interrupt OUT
Endpoint.  They will only go out the Control Endpoint.

In addition, many devices simply do not hande Feature reports sent out the
Interrupt OUT endpoint.

Reported-by:  <simon@mungewell.org>
Signed-off-by: Alan Ott <alan@signal11.us>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>