i.MX6SX uses the v6 LCDIF controller, while i.MX28 uses the older v4
version. The driver has supported the "fsl,imx6sx-lcdif" compatible string
since the initial commit:

   commit 45d59d704080 ("drm: Add new driver for MXSFB controller")

Therefore the fallback compatible string "fsl,imx28-lcdif" is not required
and can be removed.

Fix the following CHECK_DTB warning:
/arch/arm/boot/dts/nxp/imx/imx6sx-nitrogen6sx.dtb: lcdif@2220000 (fsl,imx6sx-lcdif): compatible: 'oneOf' conditional failed, one must be fixed:
        ['fsl,imx6sx-lcdif', 'fsl,imx28-lcdif'] is too long

Signed-off-by: Frank Li <Frank.Li@nxp.com>
---
Cc: Liu Ying <victor.liu@nxp.com>
Cc: Fabio Estevam <festevam@gmail.com>
Previous Fabio Estevam work try to allow fallback at
https://lore.kernel.org/imx/42eb2d42-47b0-46b6-92e9-c59473113c2d@nxp.com/ (local)
---
 arch/arm/boot/dts/nxp/imx/imx6sx.dtsi | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm/boot/dts/nxp/imx/imx6sx.dtsi b/arch/arm/boot/dts/nxp/imx/imx6sx.dtsi
index 1426f357d4744..aefae5a3a6beb 100644
--- a/arch/arm/boot/dts/nxp/imx/imx6sx.dtsi
+++ b/arch/arm/boot/dts/nxp/imx/imx6sx.dtsi

@@ -1304,7 +1304,7 @@ csi2: csi@221c000 {
 				};
 
 				lcdif1: lcdif@2220000 {
-					compatible = "fsl,imx6sx-lcdif", "fsl,imx28-lcdif";
+					compatible = "fsl,imx6sx-lcdif";
 					reg = <0x02220000 0x4000>;
 					interrupts = <GIC_SPI 5 IRQ_TYPE_EDGE_RISING>;
 					clocks = <&clks IMX6SX_CLK_LCDIF1_PIX>,

@@ -1325,7 +1325,7 @@ lcdif1_to_ldb: endpoint {
 				};
 
 				lcdif2: lcdif@2224000 {
-					compatible = "fsl,imx6sx-lcdif", "fsl,imx28-lcdif";
+					compatible = "fsl,imx6sx-lcdif";
 					reg = <0x02224000 0x4000>;
 					interrupts = <GIC_SPI 6 IRQ_TYPE_EDGE_RISING>;
 					clocks = <&clks IMX6SX_CLK_LCDIF2_PIX>,

-- 
2.43.0