imsm: Add --export option for --detail-platform

imsm: Add --export option for --detail-platform

This option will provide most of information we can get via
mdadm --detail-platform [-e format] in the key=value format.
Example output:

$ mdadm --detail-platform
       Platform : Intel(R) Matrix Storage Manager
        Version : 9.5.0.1037
    RAID Levels : raid0 raid1 raid10 raid5
    Chunk Sizes : 4k 8k 16k 32k 64k 128k
    2TB volumes : supported
      2TB disks : not supported
      Max Disks : 7
    Max Volumes : 2 per array, 4 per controller
 I/O Controller : /sys/devices/pci0000:00/0000:00:1f.2 (SATA)

$ mdadm --detail-platform --export
MD_FIRMWARE_TYPE=imsm
IMSM_VERSION=9.5.0.1037
IMSM_SUPPORTED_RAID_LEVELS=raid0 raid1 raid10 raid5
IMSM_SUPPORTED_CHUNK_SIZES=4k 8k 16k 32k 64k 128k
IMSM_2TB_VOLUMES=yes
IMSM_2TB_DISKS=no
IMSM_MAX_DISKS=7
IMSM_MAX_VOLUMES_PER_ARRAY=2
IMSM_MAX_VOLUMES_PER_CONTROLLER=4

Signed-off-by: Maciej Naruszewicz <maciej.naruszewicz@intel.com>
Signed-off-by: NeilBrown <neilb@suse.de>