drm: atmel-hlcdc: add support for DSI output formats

Add support for the following DPI mode if the encoder type
is DSI as per the XLCDC IP datasheet:
- 16BPPCFG1
- 16BPPCFG2
- 16BPPCFG3
- 18BPPCFG1
- 18BPPCFG2
- 24BPP

Signed-off-by: Manikandan Muralidharan <manikandan.m@microchip.com>
[durai.manickamkr@microchip.com: update output format using is_xlcdc flag]
Signed-off-by: Durai Manickam KR <durai.manickamkr@microchip.com>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20240424053351.589830-8-manikandan.m@microchip.com