Reserved blocks are used for storing bad block tables. With "nand bad"
command, these reserved blocks are shown as bad blocks. This is leading
to confusion when compared with Linux bad blocks. Hence, display
"bbt reserved" when printing reserved blocks with "nand bad" command.
To acheive this, return 2 which represents reserved from nand_isbad_bbt()
instead of 1 in case of reserved blocks and catch it in cmd/nand.c.
"nand bad" command display's hexadecimal numbers, so add "0x" prefix.