drm/bridge: ti-sn65dsi86: Cleanup managing of drvdata

Let's:
- Set the drvdata as soon as it's allocated. This just sets up a
  pointer so there's no downside here.
- Remove the useless call to i2c_set_clientdata() which is literally
  the same thing as dev_set_drvdata().

No functional changes intended.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20210423095743.v5.7.If5d4d4e22e97bebcd493b76765c1759527705620@changeid