ARM: ux500: Add an auxdata entry for MUSB for clock-name look-up

The recently DT:ed MUSB driver will require clock-name by device-name
look-up capability, until common clk has is properly supported by the
ux500 platform.

Acked-by: Fabio Baltieri <fabio.baltieri@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>