ARM: dts: am335x-evm: NAND: update MTD partition table

This patch has following updates, specific to MTD/NAND DT
 - update MTD NAND partition table to keep compatibility between
   different boards and mainline u-boot.
 - prefix 'NAND.' in names of NAND device MTD partitions to differentiate them
   from other MTD device partitions (like NOR and QSPI)
               Partition_Name            Partition_Size
    /dev/mtd0  NAND.SPL                  1 block-size*
    /dev/mtd1  NAND.SPL.backup1          1 block-size*
    /dev/mtd2  NAND.SPL.backup2          1 block-size*
    /dev/mtd3  NAND.SPL.backup3          1 block-size*
    /dev/mtd5  NAND.u-boot-spl-os        2 block-size* [for falcon boot]
    /dev/mtd4  NAND.u-boot               1 MB
    /dev/mtd6  NAND.u-boot-env           1 block-size*
    /dev/mtd7  NAND.u-boot-env.backup1   1 block-size*
    /dev/mtd8  NAND.kernel               till 0xA00000
    /dev/mtd9  NAND.file-system          till end of device

* am335x-evm uses NAND device with block-size=128KiB

Signed-off-by: Pekon Gupta <pekon@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>