nir: add a bit_size parameter to nir_ssa_dest_init

nir: add a bit_size parameter to nir_ssa_dest_init

v2: Squash multiple commits addressing the new parameter in different
    files so we don't break the build (Iago)

v3: Fix tgsi (Samuel)

v4: Fix nir_clone.c (Samuel)

v5: Fix vc4 and freedreno (Iago)

v6 (Sam)
- Fix build errors in nir_lower_indirect_derefs
- Use helper to get type size from nir_alu_type.

Signed-off-by: Iago Toral Quiroga <itoral@igalia.com>
Signed-off-by: Samuel Iglesias Gonsalvez <siglesias@igalia.com>
Tested-by: Rob Clark <robdclark@gmail.com>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Reviewed-by: Samuel Iglesias Gonsálvez <siglesias@igalia.com>
Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>