tgsi/mesa: handle KERNEL case

Translate to compute for now.

Acked-by: Roland Scheidegger <sroland@vmware.com>

src/gallium/auxiliary/tgsi/tgsi_from_mesa.h

@@ -62,6 +62,7 @@ pipe_shader_type_from_mesa(gl_shader_stage stage)
    case MESA_SHADER_FRAGMENT:
       return PIPE_SHADER_FRAGMENT;
    case MESA_SHADER_COMPUTE:
+   case MESA_SHADER_KERNEL:
       return PIPE_SHADER_COMPUTE;
    default:
       unreachable("bad shader stage");