Have you tried the uboot parameter pass to the kernel.
you need to tell kernel the "if" is RGB24.
video=mxcfb0:dev=ldb,bpp=32,if=RGB24
For the timing for the LVDS panel, please check the devices tree bindiing guide.
And make changes according to the datasheet of the lvds panel.
Documentation/devicetree/bindings/staging/imx-drm/ldb.txt
Documentation/devicetree/bindings/video/display-timing.txt
Actually, the uboot "if" also can use the fsl,data-width in device tree to define.