st/mesa: convert the ETC1 format to an uncompressed one if unsupported

I don't know of any hardware which supports it.
With this, GL_OES_compressed_ETC1_RGB8_texture is supported if RGBA8
is supported.

Reviewed-by: Glenn Kennard <glenn.kennard@gmail.com>
diff --git a/docs/relnotes/10.3.html b/docs/relnotes/10.3.html
index c0828da..a1f2777 100644
--- a/docs/relnotes/10.3.html
+++ b/docs/relnotes/10.3.html
@@ -60,6 +60,7 @@
 <li>GL_ARB_fragment_layer_viewport on nv50, nvc0, llvmpipe, r600</li>
 <li>GL_AMD_vertex_shader_viewport_index on i965/gen7+, r600</li>
 <li>GL_ARB_clear_texture on i965</li>
+<li>GL_OES_compressed_ETC1_RGB8_texture on nv30, nv50, nvc0, r300, r600, radeonsi, softpipe, llvmpipe</li>
 <li>A new software rasterizer driver (kms_swrast_dri.so) that works with
 DRM drivers that don't have a full-fledged GEM (such as qxl or simpledrm)</li>
 </ul>