ARM: at91/dt: fix USB high-speed clock to select UTMI

The UTMI clock must be selected by any high-speed USB IP. The logic behind it
needs this particular clock.
So, correct the clock in the device tree files affected.

Reported-by: Bo Shen <voice.shen@atmel.com>
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Cc: <stable@vger.kernel.org> #3.18