spi: zynq_spi: Add fdt support in driver

Now zynq spi driver platform data is controlled by devicetree,
enable the status by saying "okay" on respective board dts to use
the devicetree generated platdata.

Ex:
&spi1 {
	status = "okay";
};

Signed-off-by: Jagan Teki <jteki@openedev.com>
Acked-by: Simon Glass <sjg@chromium.org>
Cc: Michal Simek <michal.simek@xilinx.com>
Cc: Siva Durga Prasad Paladugu <sivadur@xilinx.com>
Tested-by: Jagan Teki <jteki@openedev.com>
diff --git a/doc/device-tree-bindings/spi/spi-zynq.txt b/doc/device-tree-bindings/spi/spi-zynq.txt
index a7c2757..f397a36 100644
--- a/doc/device-tree-bindings/spi/spi-zynq.txt
+++ b/doc/device-tree-bindings/spi/spi-zynq.txt
@@ -11,6 +11,7 @@
 - clocks		: Clock phandles (see clock bindings for details).
 - clock-names		: List of input clock names - "ref_clk", "pclk"
 			  (See clock bindings for details).
+- spi-max-frequency	: Maximum SPI clocking speed of device in Hz
 
 Example:
 
@@ -22,6 +23,7 @@
 		interrupts = <0 26 4>;
 		clocks = <&clkc 25>, <&clkc 34>;
 		clock-names = "ref_clk", "pclk";
+		spi-max-frequency = <166666700>;
 		#address-cells = <1>;
 		#size-cells = <0>;
 	} ;