dt-bindings: display: bridge: ldb: Add i.MX93 LDB

Same to i.MX8mp LDB, i.MX93 LDB is controlled by mediamix blk-ctrl
through 'ldb' register and 'lvds' register.  Also, the 'ldb' clock
is required.  i.MX93 LDB supports only one LVDS channel(channel 0,
a.k.a, LVDS Channel-A in the device tree binding documentation), while
i.MX8mp LDB supports at most two.  Add i.MX93 LDB device tree binding
in the existing i.MX8mp LDB device tree binding documentation.

Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Liu Ying <victor.liu@nxp.com>
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20230123021449.969243-2-victor.liu@nxp.com