[new uImage] Add new uImage format handling to other bootm related commands

Updated commands:

docboot  - cmd_doc.c
fdcboot  - cmd_fdc.c
diskboot - cmd_ide.c
nboot    - cmd_nand.c
scsiboot - cmd_scsi.c
usbboot  - cmd_usb.c

Signed-off-by: Marian Balakowicz <m8@semihalf.com>