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/glsl/glsl_to_nir.cpp

@@ -2090,7 +2090,7 @@ nir_visitor::visit(ir_expression *ir)
    case ir_unop_get_buffer_size: {
       nir_intrinsic_instr *load = nir_intrinsic_instr_create(
          this->shader,
-         nir_intrinsic_get_buffer_size);
+         nir_intrinsic_get_ssbo_size);
       load->num_components = ir->type->vector_elements;
       load->src[0] = nir_src_for_ssa(evaluate_rvalue(ir->operands[0]));
       unsigned bit_size = glsl_get_bit_size(ir->type);