Previously, we've set element_size == 16 which causes loads from
packed vec3 arrays to cross the boundary and return wrong data.
This patch sets element_size = 4 and splits loads into single channel.
Fixes all of dEQP-VK.subgroups.ballot_broadcast.*
Cc: 20.1 <mesa-stable@lists.freedesktop.org>
Reviewed-by: Rhys Perry <pendingchaos02@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5977>
(cherry picked from commit 7015d2c249)
2646170bcd