drm/v3d: Move perfmon init completely into own unit

Now that the build time dependencies on various array sizes have been
removed, we can move the perfmon init completely into its own compilation
unit and remove the hardcoded defines.

This improves on the temporary fix quickly delivered in commit
9c3951ec ("drm/v3d: Fix perfmon build error/warning").

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@igalia.com>
References: 9c3951ec ("drm/v3d: Fix perfmon build error/warning")
Reviewed-by: Maíra Canal <mcanal@igalia.com>
Signed-off-by: Maíra Canal <mcanal@igalia.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240711135340.84617-10-tursulin@igalia.com