drm: lcdif: Add i.MX93 LCDIF compatible string

With all previous preparations done to make it possible for the
single LCDIF embedded in i.MX93 SoC to drive multiple displays
simultaneously, add i.MX93 LCDIF compatible string as the last
step of adding i.MX93 LCDIF support.

Tested-by: Alexander Stein <alexander.stein@ew.tq-group.com>
Reviewed-by: Alexander Stein <alexander.stein@ew.tq-group.com>
Reviewed-by: Marek Vasut <marex@denx.de>
Signed-off-by: Liu Ying <victor.liu@nxp.com>
Signed-off-by: Marek Vasut <marex@denx.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20230510092450.4024730-7-victor.liu@nxp.com