vrend, caps: multisample images are not available on GLES

Consequently calling  glGetIntegerv with GL_MAX_IMAGE_SAMPLES would results
in an error  state on GLES that is not cleaned up and this has
consequences for the following processing.

Closes: #28

Fixes: 950de33c32
   renderer: add image support. (v4)

Signed-off-by: Gert Wollny <gert.wollny@collabora.com>
Reviewed-by: Jakob Bornecrantz <jakob@collabora.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

src/vrend_renderer.c

@@ -8139,7 +8139,8 @@ static void vrend_renderer_fill_caps_v2(int gl_ver, int gles_ver,  union virgl_c
          max = PIPE_MAX_SHADER_IMAGES;
       caps->v2.max_shader_image_frag_compute = max;
 
-      glGetIntegerv(GL_MAX_IMAGE_SAMPLES, (GLint*)&caps->v2.max_image_samples);
+      if (gl_ver > 0) /* Seems GLES doesn't support multisample images */
+         glGetIntegerv(GL_MAX_IMAGE_SAMPLES, (GLint*)&caps->v2.max_image_samples);
    }
 
    if (has_feature(feat_storage_multisample))