cmd_nand.c: Fix 'nand dump' after latest MTD resync

cmd_nand.c: Fix 'nand dump' after latest MTD resync

With 2a8e0fc nand_do_read_ops changed in behavior slightly (keeping in sync
with the kernel which did this change in b64d39d8) such that the OOB data is
always copied into oobbuf and never appended to datbuf.  Within U-Boot only
the nand_dump function (for the dump nand subcommand) was expecting the OOB
data to only be appended to datbuf.  So we now change nand_dump to not
malloc extra space, correct the comment about datbuf and OOB data and switch
the pointer to oobbuf before printing.

Cc: Scott Wood <scottwood@freescale.com>
Signed-off-by: Tom Rini <trini@ti.com>
Signed-off-by: Scott Wood <scottwood@freescale.com>