USB: gadget: fix EEM gadget CRC usage

eem_wrap() is sending a sentinel CRC, but it didn't indicate that to
the host, it should zero bit 14 (bmCRC) in the EEM packet header,
instead of setting it.

Also remove a redundant crc calculation in eem_unwrap().


Signed-off-by: Steve Longerbeam <stevel@netspectrum.com>
Acked-by: Brian Niebuhr <bniebuhr@efjohnson.com>
Acked-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>