USB: minor fixes for r8a66597 driver

This patch (as967) makes a few relatively minor changes to the
r8a66597 driver:

	finish_request() does nothing but call done(), so merge the
	two routines.

	Detect and report -EOVERFLOW errors.

	Fix the calculation that checks for short packets.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
CC: Yoshihiro Shimoda <shimoda.yoshihiro@renesas.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>