arm: mmp: remove clock name from usb pdata for ttc

The clock name will directly get by driver. Removing
the name from pdata.

Acked-by: Haojian Zhuang <haojian.zhuang@gmail.com>
Signed-off-by: Chao Xie <chao.xie@marvell.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>