[POWERPC] fsl_spi: stop using device_type = "spi"

Also:
- rename "fsl_spi" to "fsl,spi";
- add and use cell-index property, if found;
- split probing code out of fsl_spi_init, thus we can call
  it for legacy device_type probing and new "compatible" probing.

Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
diff --git a/arch/powerpc/boot/dts/sbc8349.dts b/arch/powerpc/boot/dts/sbc8349.dts
index 9c13c1a..0934f54 100644
--- a/arch/powerpc/boot/dts/sbc8349.dts
+++ b/arch/powerpc/boot/dts/sbc8349.dts
@@ -87,7 +87,8 @@
 		};
 
 		spi@7000 {
-			compatible = "fsl_spi";
+			cell-index = <0>;
+			compatible = "fsl,spi";
 			reg = <0x7000 0x1000>;
 			interrupts = <0x10 0x8>;
 			interrupt-parent = <&ipic>;