USB: Fix speed detection on EHCI cntr with root hub transaction translators

This patch fixes an issue that the speed of USB devices was not detected
correctly on some EHCI controllers. This will be used on the upcoming VCT
EHCI support.

Signed-off-by: Stefan Roese <sr@denx.de>
Signed-off-by: Remy Bohmer <linux@bohmer.net>