drm: meson: venc: use proper macros instead of magic constants

This patch add new macros which are used to set the following
registers:
- ENCI_CFILT_CTRL
- ENCI_CFILT_CTRL2
- ENCI_MACV_MAX_AMP
- ENCI_VIDEO_MODE_ADV
- ENCI_VFIFO2VD_CTL
- ENCI_VIDEO_EN
- ENCP_VIDEO_MODE
- VPU_HDMI_SETTING
- VENC_UPSAMPLE_CTRL0
- VENC_UPSAMPLE_CTRL1
- VENC_UPSAMPLE_CTRL2
- VENC_VDAC_FIFO_CTRL
- VENC_VDAC_DAC0_FILT_CTRL0
- VENC_INTCTRL

Signed-off-by: Julien Masson <jmasson@baylibre.com>
Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Link: https://patchwork.freedesktop.org/patch/msgid/86r27j82ef.fsf@baylibre.com