tu: Use tu_cs_add_entries() with non-render-pass secondaries

tu: Use tu_cs_add_entries() with non-render-pass secondaries

Even though vkCmdRenderPassBegin() isn't allowed inside a secondary
command buffer, vkCmdDispatch() is, and we emit an IB with compute
dispatches, which means that if the secondary command buffer records a
vkCmdDispatch() then we'll have an IB inside an IB, which is illegal.
Fixes hangs in e.g.
dEQP-VK.api.command_buffers.record_simul_use_secondary_one_primary.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4605>