drm: bridge: dw-hdmi: set ddc scl clock rate according to dts

drm: bridge: dw-hdmi: set ddc scl clock rate according to dts

To set dw hdmi i2c bus adapter scl clock rate, we introduce two device
tree parameter, ddc-i2c-scl-high-time-ns and ddc-i2c-scl-low-time-ns.

ddc-i2c-scl-high-time-ns: how many ns SCL hold high
ddc-i2c-scl-low-time-ns: how many ns SCL hold low

After measurement, 50KHz scl clock rate recommended configuration is:

&hdmi {
	ddc-i2c-scl-high-time-ns = <9625>;
	ddc-i2c-scl-low-time-ns = <10000>;
};

100KHz recommended configuration is:
&hdmi {
        ddc-i2c-scl-high-time-ns = <4708>;
        ddc-i2c-scl-low-time-ns = <4916>;
};

If dts parameter is not available, the default scl rate is 100KHz.

Change-Id: I6f6b0bf1694ab59e70da789ead99e15a53c93e4d
Signed-off-by: Zheng Yang <zhengyang@rock-chips.com>