rockchip: remove no needed code for rk3399

rockchip: remove no needed code for rk3399

We have do something for clocks gate.

Fox example as the below:
susped:
clk_gate_con_save();
clk_gate_con_disable();

resume:
clk_gate_con_restore();
--

SO, add the plls_suspend_prepare() and plls_resume_finish() are not
necessary to S2R, that will save S2R time if remove them.

BRANCH=none
BUG=chrome-os-partner:58870,chrome-os-partner:55934
TEST=build kevin, two dogfooders with suspend_stress_test
passing 3000 cycles and still going on.

Change-Id: Icfbabc0b3ea8d2b5108d4f3de99a803b6d459669
Signed-off-by: Caesar Wang <wxt@rock-chips.com>