drm/bridge: ti-sn65dsi86: Code motion of refclk management functions

No functional changes--this just makes the diffstat of a future change
easier to understand.

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.v5.12.I047b8c7c6a3fc60eaca473da7a374f171fb021c2@changeid