dt-bindings: watchdog: fsl-imx-wdt: add compatible string fsl,ls1021a-wdt

Add compatible string fsl,ls1021a-wdt for ls1021a SoC. fsl,ls1021a-wdt
allow big-endian property.

Signed-off-by: Frank Li <Frank.Li@nxp.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20250522194732.493624-1-Frank.Li@nxp.com


Signed-off-by: Rob Herring (Arm) <robh@kernel.org>