drm/msm/dp: parse DT from dp_parser_get

It makes little sense to split the submodule get and actual DT parsing.
Call dp_parser_parse() directly from dp_parser_get(), so that the parser
data is fully initialised once it is returned to the caller.

Reviewed-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Tested-by: Kuogee Hsieh <quic_khsieh@quicinc.com>
Reviewed-by: Kuogee Hsieh <quic_khsieh@quicinc.com>
Patchwork: https://patchwork.freedesktop.org/patch/576101/
Link: https://lore.kernel.org/r/20240126-dp-power-parser-cleanup-v3-3-098d5f581dd3@linaro.org