arm/mx2: use cpp magic to create spi_imx devices

This makes the source shorter and easier to verify.  While at it switch
to use the SoC-prefixed constants.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
diff --git a/arch/arm/mach-mx2/devices.h b/arch/arm/mach-mx2/devices.h
index 97306aa..e13a352 100644
--- a/arch/arm/mach-mx2/devices.h
+++ b/arch/arm/mach-mx2/devices.h
@@ -25,6 +25,8 @@
 extern struct platform_device mxc_usbh2;
 extern struct platform_device mxc_spi_device0;
 extern struct platform_device mxc_spi_device1;
+#ifdef CONFIG_MACH_MX27
 extern struct platform_device mxc_spi_device2;
+#endif
 extern struct platform_device imx_ssi_device0;
 extern struct platform_device imx_ssi_device1;