ARM: dts: imx: replace undocumented compatible string edt,edt-ft5x06 with edt,edt...

ARM: dts: imx: replace undocumented compatible string edt,edt-ft5x06 with edt,edt-ft5206

The edt,edt-ft5x06 compatible is not referenced in
drivers/input/touchscreen/edt-ft5x06.c and is not documented.

There is no publicly available datasheet or binding information that
distinguishes edt-ft5206/ft5306/ft5406 variants and the driver treats these
FT5x06-family controllers with the same configuration model. So switch to
the lowest common and documented baseline compatible edt,edt-ft5206.

Fix below CHECK_DTBS warnings:
arch/arm/boot/dts/nxp/imx/imx53-m53menlo.dtb: /soc/bus@60000000/i2c@63fc8000/touchscreen@38: failed to match any schema with compatible: ['edt,edt-ft5x06']

ABI impact consideration:
Not affect Linux kernel. The I2C subsystem uses a legacy fallback mechanism
where it strips the vendor prefix from the compatible string to derive the
client name, resulting in edt-ft5x06

	{ .name = "edt-ft5x06", .driver_data = (long)&edt_ft5x06_data },

After this, the driver was actively binding to these devices based on the
compatible string.

Known user (U-Boot) does not parse or use edt,edt-ft* touchscreen
compatibles.

Signed-off-by: Frank Li <Frank.Li@nxp.com>