The DDC preamble and target address only need to be set once before
reading the EDID, even if multiple segments have to be read.

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Reviewed-by: Robert Foss <robert.foss@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20221214125821.12489-9-paul@crapouillou.net