powerpc/corenet_ds: add back buffer write for NOR flash

Enable buffer write for better performance. This platform uses a NOR flash
chip which supports write buffer programming. CFI driver can query the
buffer size and use it to program the flash for best performance.

Signed-off-by: York Sun <yorksun@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>

include/configs/corenet_ds.h

@@ -73,6 +73,7 @@
 #else
 #define CONFIG_FLASH_CFI_DRIVER
 #define CONFIG_SYS_FLASH_CFI
+#define CONFIG_SYS_FLASH_USE_BUFFER_WRITE
 #endif
 
 #if defined(CONFIG_SPIFLASH)