amd/vpelib: Reformat index variables and update enum

Reformat index variables to indicate loop specifics and update enum to match formatting guide.

Signed-off-by: Brendan Steve Leder <Brendansteve.Leder@amd.com>
Reviewed-by: Roy Chan <Roy.Chan@amd.com>
Reviewed-by: Evan Damphousse <Evan.Damphousse@amd.com>
Acked-by: Alan Liu <Haoping.Liu@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/33833>
9 files changed