powerpc: add fsl,fifo-depth property to Freescale SSI device nodes

The Freescale Serial Synchronous Interface (SSI) is an audio device present on
some Freescale SOCs.  Various implementations of the SSI have a different
transmit and receive FIFO depth, but are otherwise identical.  To support
these variations, add a new property fsl,fifo-depth to the SSI node that
specifies the depth of the FIFOs.

Also update the MPC8610 HPCD device tree with this property.
Signed-off-by: Timur Tabi <timur@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>

Documentation/powerpc/dts-bindings/fsl/ssi.txt

@@ -30,6 +30,8 @@ Required properties:
 - fsl,capture-dma:  phandle to a node for the DMA channel to use for
                     capture (recording) of audio.  This is typically dictated
                     by SOC design.  See the notes below.
+- fsl,fifo-depth:   the number of elements in the transmit and receive FIFOs.
+                    This number is the maximum allowed value for SFCSR[TFWM0].
 
 Optional properties:
 - codec-handle	  : phandle to a 'codec' node that defines an audio

arch/powerpc/boot/dts/mpc8610_hpcd.dts

@@ -217,6 +217,7 @@ ssi@16000 {
 			codec-handle = <&cs4270>;
 			fsl,playback-dma = <&dma00>;
 			fsl,capture-dma = <&dma01>;
+			fsl,fifo-depth = <8>;
 		};
 
 		ssi@16100 {
@@ -225,6 +226,7 @@ ssi@16100 {
 			reg = <0x16100 0x100>;
 			interrupt-parent = <&mpic>;
 			interrupts = <63 2>;
+			fsl,fifo-depth = <8>;
 		};
 
 		dma@21300 {