USB: fix PS3 EHCI systems

After commit aaa0ef28 "PS3 EHCI QH
read work-around", Terratec Grabby (em28xx) stopped working with AMD
Geode LX 800 (USB controller AMD CS5536). Since this is a PS3 only
fix, the following patch adds a conditional block around it.

Signed-off-by: Ricardo Martins <rasm@fe.up.pt>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>