drm/mcde: Retry DSI read/write transactions

The vendor driver makes a few retries on read DSI
transactions, something that is needed especially in
case of read (such as reading the panel MTP ID) while
the panel is running in video mode. This happens on
the Samsung s6e63m0 panel on the Golden device.

Retry reads and writes alike three times.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Stephan Gerhold <stephan@gerhold.net>
Cc: Stephan Gerhold <stephan@gerhold.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20200814194451.3494294-1-linus.walleij@linaro.org