drm/v3d: Add some local variables in queries/extensions

Add some local variables to make the code a bit less verbose, with the
main benefit being pulling some lines to under 80 columns wide.

Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@igalia.com>
Reviewed-by: Maíra Canal <mcanal@igalia.com>
Signed-off-by: Maíra Canal <mcanal@igalia.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240711135340.84617-12-tursulin@igalia.com