dfu: allow to manage DFU on several devices

dfu: allow to manage DFU on several devices

Add support of DFU for several interface/device
with one command.

The format for "dfu_alt_info" in this case is :
- <interface> <dev>'='alternate list (';' separated)
- each interface is separated by '&'

The previous behavior is always supported.

One example for NOR (bootloaders) + NAND (rootfs in UBI):

U-Boot> env set dfu_alt_info \
"sf 0:0:10000000:0=spl part 0 1;u-boot part 0 2; \
u-boot-env part 0 3&nand 0=UBI partubi 0,3"

U-Boot> dfu 0 list

DFU alt settings list:
dev: SF alt: 0 name: spl layout: RAW_ADDR
dev: SF alt: 1 name: ssbl layout: RAW_ADDR
dev: SF alt: 2 name: u-boot-env layout: RAW_ADDR
dev: NAND alt: 3 name: UBI layout: RAW_ADDR

U-Boot> dfu 0

$> dfu-util -l

Found DFU: [0483:5720] ver=9999, devnum=96, cfg=1,\
 intf=0, alt=3, name="UBI", serial="002700333338511934383330"
Found DFU: [0483:5720] ver=9999, devnum=96, cfg=1,\
 intf=0, alt=2, name="u-boot-env", serial="002700333338511934383330"
Found DFU: [0483:5720] ver=9999, devnum=96, cfg=1,\
 intf=0, alt=1, name="u-boot", serial="002700333338511934383330"
Found DFU: [0483:5720] ver=9999, devnum=96, cfg=1,\
 intf=0, alt=0, name="spl", serial="002700333338511934383330"

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>