nir: Rename get_buffer_size to get_ssbo_size

This makes it explicit that this intrinsic is only for SSBOs.  For the
v3dv driver, we'll be adding a get_ubo_size intrinsic and we want to be
able to distinguish between the two.

Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>
Reviewed-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6812>

src/compiler/spirv/vtn_variables.c

@@ -2818,7 +2818,7 @@ vtn_handle_variables(struct vtn_builder *b, SpvOp opcode,
 
       nir_intrinsic_instr *instr =
          nir_intrinsic_instr_create(b->nb.shader,
-                                    nir_intrinsic_get_buffer_size);
+                                    nir_intrinsic_get_ssbo_size);
       instr->src[0] = nir_src_for_ssa(ptr->block_index);
       nir_ssa_dest_init(&instr->instr, &instr->dest, 1, 32, NULL);
       nir_builder_instr_insert(&b->nb, &instr->instr);