drm/msm/dsi_pll_10nm: Convert pr_err prints to DRM_DEV_ERROR

DRM_DEV_ERROR should be used across this entire source: convert the
pr_err prints to the first as a cleanup.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@somainline.org>
Signed-off-by: Rob Clark <robdclark@chromium.org>