mach-ux500: update MUSB clock configurations

MUSB driver has been updated to separate out BSP layer
from its generic parts, as separate driver. This patch
configures the clock with the new platform driver name.

Signed-off-by: Mian Yousaf Kaukab <mian-yousaf.kaukab@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>