dt-bindings: firmware: Remove xlnx,zynqmp-firmware.txt file

The funtionality of xlnx,zynqmp-firmware.txt is replaced with
xlnx,zynqmp-firmware.yaml bindings so this patch removes the
zynqmp-firmware.txt file

Reviewed-by: Rob Herring <[e-mail]>
Signed-off-by: Nava kishore Manne <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

Documentation/devicetree/bindings/firmware/xilinx/xlnx,zynqmp-firmware.txt

···
------------------------------------------------------------------
-Device Tree Bindings for the Xilinx Zynq MPSoC Firmware Interface
------------------------------------------------------------------
-
-The zynqmp-firmware node describes the interface to platform firmware.
-ZynqMP has an interface to communicate with secure firmware. Firmware
-driver provides an interface to firmware APIs. Interface APIs can be
-used by any driver to communicate to PMUFW(Platform Management Unit).
-These requests include clock management, pin control, device control,
-power management service, FPGA service and other platform management
-services.
-
-Required properties:
- - compatible:	Must contain any of below:
-		"xlnx,zynqmp-firmware" for Zynq Ultrascale+ MPSoC
-		"xlnx,versal-firmware" for Versal
- - method:	The method of calling the PM-API firmware layer.
-		Permitted values are:
-		  - "smc" : SMC #0, following the SMCCC
-		  - "hvc" : HVC #0, following the SMCCC
-
--------
-Example
--------
-
-Zynq Ultrascale+ MPSoC
-----------------------
-firmware {
-	zynqmp_firmware: zynqmp-firmware {
-		compatible = "xlnx,zynqmp-firmware";
-		method = "smc";
-		...
-	};
-};
-
-Versal
-------
-firmware {
-	versal_firmware: versal-firmware {
-		compatible = "xlnx,versal-firmware";
-		method = "smc";
-		...
-	};
-};