configs: at91: sama5: 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/sama5d3_xplained_nandflash_defconfig b/configs/sama5d3_xplained_nandflash_defconfig
index 2468df9..62716b6 100644
--- a/configs/sama5d3_xplained_nandflash_defconfig
+++ b/configs/sama5d3_xplained_nandflash_defconfig
@@ -17,7 +17,7 @@
 CONFIG_NAND_BOOT=y
 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"
+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"
 # CONFIG_DISPLAY_BOARDINFO is not set
 CONFIG_HUSH_PARSER=y
 CONFIG_CMD_BOOTZ=y