ARM: dts: imx6qdl-sabresd: Pass the hannstar panel compatible string

It is preferred to use the panel compatible string rather than passing the
LCD timings in the device tree.

So pass the "hannstar,hsd100pxn1" compatible string to describe
the LVDS panel on this board.

Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>