Gigabeat S: Implement LCD contrast, invert and flip modes. Enhance LCD power management. Include init data but it's not needed yet (identical to Gigabeat F).

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@26154 a1c6a512-1295-4272-9138-f99709370657

firmware/target/arm/imx31/spi-imx31.c

@@ -435,3 +435,9 @@ bool spi_transfer(struct spi_transfer_desc *xfer)
 
     return retval;
 }
+
+/* Returns 'true' if the descriptor is not busy */
+bool spi_transfer_complete(const struct spi_transfer_desc *xfer)
+{
+    return xfer->next == NULL;
+}