drm: drmGetDevice return correct device on multi GPU setups

Currently drmGetDevice always returns the first device it finds under
/dev/dri/.

Move the target device to the start of the list during iteration. This
way during deduplication it'll preserve its place and will be returned
to the user.

v2: Keep the memory leak separate.
v3: Move the drmFoldDuplicatedDevices description

Signed-off-by: Qiang Yu <Qiang.Yu@amd.com>
[Emil Velikov: move drmFoldDuplicatedDevices description, add
changelog, reword commit message]
Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>