broadcom/compiler: add lowering pass to scalarize non 32-bit general load/store

broadcom/compiler: add lowering pass to scalarize non 32-bit general load/store

V3D hardware doesn't support vector access for general TMU load/store
operations like the ones we use for UBO and SSBO, so we need to split
these to scalar operations.

It should be noted that we also have a vectorization pass (which runs
later, during optimization), that may reconstruct some of these into
32-bit operations when possible (i.e. when the resulting operation
is 32-bit aligned).

Reviewed-by: Alejandro Piñeiro <apinheiro@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/14648>