UPSTREAM: clk: rockchip: remove redundant checking of device_node

UPSTREAM: clk: rockchip: remove redundant checking of device_node

rockchip_clk_of_add_provider is used by sub-clk driver which
already call of_iomap before calling it. If device_node does
not exist, of_iomap returns NULL which will fail to init the
sub-clk driver. So really it's redundant.

Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>
(cherry picked from git.kernel.org mmind/linux-rockchip.git
v4.7-clk/next commit a96edf5a5243e1bdf642492b783221aa498f1e49)

Change-Id: I9a51ed269fe26742da2ae84d99cf9689f49add1b
Signed-off-by: Xing Zheng <zhengxing@rock-chips.com>