radv: remove call to nir_lower_pack()

The pack_* instructions are now lowered via nir_lower_alu_to_scalar()
and unpack_* are not lowered anymore.

These bitcasts are no-ops, and lowering prevents
some optimizations like vectorization.

Note: There are still some *_split variations remaining
from different other NIR passes.

Reviewed-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6527>
diff --git a/src/amd/vulkan/radv_shader.c b/src/amd/vulkan/radv_shader.c
index f48438d..7804cd1 100644
--- a/src/amd/vulkan/radv_shader.c
+++ b/src/amd/vulkan/radv_shader.c
@@ -183,7 +183,6 @@
 		NIR_PASS(progress, shader, nir_shrink_vec_array_vars, nir_var_function_temp);
 
                 NIR_PASS_V(shader, nir_lower_vars_to_ssa);
-		NIR_PASS_V(shader, nir_lower_pack);
 
 		if (allow_copies) {
 			/* Only run this pass in the first call to