clk: mmp: add reset support

Some clock control regsiter has bit to reset the cotroller.
So before enable the clock, we need deassert the reset pin.
Make use of reset controller framework to export reset interface
for device drivers, then device driver can control the reset action.

Signed-off-by: Chao Xie <chao.xie@marvell.com>
Acked-by: Haojian Zhuang <haojian.zhuang@gmail.com>
Signed-off-by: Michael Turquette <mturquette@linaro.org>