configs: at91sam9x5ek: updated mtdparts variable in bootargs

We have a new demo layout of our sama5 boards for the NAND Flash
memory.
According to this new layout, adjust the mtdparts variable in bootargs
to align with this, which is available at :
http://www.at91.com/linux4sam/bin/view/Linux4SAM/Sama5d3XplainedMainPage#NAND_Flash_demo_Memory_map,

Based on original work by Wenyou Yang

Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>
diff --git a/configs/at91sam9x5ek_dataflash_defconfig b/configs/at91sam9x5ek_dataflash_defconfig
index ffed179..a888e9d 100644
--- a/configs/at91sam9x5ek_dataflash_defconfig
+++ b/configs/at91sam9x5ek_dataflash_defconfig
@@ -8,7 +8,7 @@
 CONFIG_SYS_EXTRA_OPTIONS="SYS_USE_DATAFLASH"
 CONFIG_BOOTDELAY=3
 CONFIG_USE_BOOTARGS=y
-CONFIG_BOOTARGS="console=ttyS0,115200 earlyprintk mtdparts=atmel_nand:256k(bootstrap)ro,512k(uboot)ro,256k(env),256k(env_redundant),256k(spare),512k(dtb),6M(kernel)ro,-(rootfs) rootfstype=ubifs ubi.mtd=7 root=ubi0:rootfs rw"
+CONFIG_BOOTARGS="console=ttyS0,115200 earlyprintk mtdparts=atmel_nand:256k(bootstrap)ro,768k(uboot)ro,256k(env_redundant),256k(env),512k(dtb),6M(kernel)ro,-(rootfs) rootfstype=ubifs ubi.mtd=6 root=ubi0:rootfs rw"
 # CONFIG_CONSOLE_MUX is not set
 CONFIG_SYS_CONSOLE_IS_IN_ENV=y
 # CONFIG_DISPLAY_BOARDINFO is not set