drm/v3d: Create function to update a set of GPU stats

Given a set of GPU stats, that is, a `struct v3d_stats` related to a
queue in a given context, create a function that can update this set
of GPU stats.

Signed-off-by: Maíra Canal <mcanal@igalia.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@igalia.com>
Reviewed-by: Jose Maria Casanova Crespo <jmcasanova@igalia.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240420213632.339941-5-mcanal@igalia.com