drm/exynos/hdmi: refactor infoframe code

Use core helpers to generate infoframes and generate vendor frame if necessary.

Changelog:
- changed 'ret >= 0' checks to '!ret'

Signed-off-by: Andrzej Hajda <a.hajda@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>