The Performance Counters enum used to identify the index of each
performance counter and provide the total number of performance
counters (V3D_PERFCNT_NUM). But, this enum is only valid for V3D 4.2,
not for V3D 7.1.

As we implemented a new flexible structure to retrieve performance
counters information, we can deprecate this enum.
Signed-off-by: Maíra Canal <mcanal@igalia.com>
Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240512222655.2792754-7-mcanal@igalia.com