drm/v3d: Use V3D_MAX_COUNTERS instead of V3D_PERFCNT_NUM

V3D_PERFCNT_NUM represents the maximum number of performance counters
for V3D 4.2, but not for V3D 7.1. This means that, if we use
V3D_PERFCNT_NUM, we might go out-of-bounds on V3D 7.1.

Therefore, use the number of performance counters on V3D 7.1 as the
maximum number of counters. This will allow us to create arrays on the
stack with reasonable size. Note that userspace must use the value
provided by DRM_V3D_PARAM_MAX_PERF_COUNTERS.

Signed-off-by: Maíra Canal <mcanal@igalia.com>
Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240512222655.2792754-6-mcanal@igalia.com