mtd: spi_flash_free()

dfu_free_entities() invoking dfu_free_entity_sf() has let to segementation
faults due to double freeing the same device.

spi_flash_free() is not relevant for the driver model but exists only for
compatibility with old drivers.

We must not remove any device here:

* The device may still be referenced.
* We don't want to have to probe again.

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
diff --git a/include/spi_flash.h b/include/spi_flash.h
index 85cae32..478c543 100644
--- a/include/spi_flash.h
+++ b/include/spi_flash.h
@@ -97,7 +97,9 @@
 				  unsigned int max_hz, unsigned int spi_mode);
 
 /* Compatibility function - this is the old U-Boot API */
-void spi_flash_free(struct spi_flash *flash);
+static inline void spi_flash_free(struct spi_flash *flash)
+{
+}
 
 static inline int spi_flash_read(struct spi_flash *flash, u32 offset,
 				 size_t len, void *buf)