cmd, nand: fix broken output of "nand info"

cmd, nand: fix broken output of "nand info"

If the value of either "nand options" or "bbt options" has a zero in
the most significant nibble, the '0x' prefix will be isolated from the
value like shown below:
|Device 0: nand0, sector size 128 KiB
|  Page size       2048 b
|  OOB size          64 b
|  Erase size    131072 b
|  subpagesize     2048 b
|  options     0x40000200
|  bbt options 0x   60000

Change the format string to produce leading zeroes filling the gap.

Signed-off-by: Lothar Waßmann <LW@KARO-electronics.de>