drm/bridge: lt9611: fix clock calculation

drm/bridge: lt9611: fix clock calculation

[ Upstream commit d7e20fb3e7db4acd45375dbf750907e3ff4bd52e ]

Instead of having several fixed values for the pcr register, calculate
it before programming. This allows the bridge to support most of the
display modes.

Fixes: 4e9e2250396c ("drm/bridge: Introduce LT9611 DSI to HDMI bridge")
Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20230118081658.2198520-6-dmitry.baryshkov@linaro.org
Signed-off-by: Sasha Levin <sashal@kernel.org>