USB: ene_usb6250: implement REQUEST SENSE

In the ene_usb6250 sub-driver for usb-storage, there is no support for
the REQUEST SENSE command.  This command is issued whenever a failure
occurs, and without it the driver has no way to tell the SCSI core
what the reason for the failure was.

This patch adds a do_scsi_request_sense() routine to the driver.  The
new routine reports the error code stored by the previous command.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Reported-and-tested-by: Andreas Hartmann <andihartmann@01019freenet.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>