[BUG] multipath-tools: 0 cyl reported on large disks due to overflow

Hi,

An integer overflow occurs in libmultipath/discovery.c:get_geometry() when
querying geometry on large disks resulting in "0 cyl" being reported:

# multipath -ll -d -v3
... | sdgm: 0 cyl, 64 heads, 32 sectors/track, start at 0

# fdisk -l /dev/sdgm
Disk /dev/sdgm: 12 TiB, 13194139533312 bytes, 25769803776 sectors
Units: sectors of 1 * 512 = 512 bytes

# dmesg | grep sdgm
sd 5:0:3:100: [sdgm] 25769803776 512-byte logical blocks: (13.2 TB/12.0TiB)


The root cause is that struct hd_geometry, from libmultipath/structs.h,
defines cylinders as an unsigned short.

Since it is a legacy interface, it should either sanitize the log output
or avoid relying on CHS geometry for large devices.