freedreno: Stop exposing MSAA image load/store on desktop GL.

GLES doesn't support it, and blob VK doesn't support it.  We could
theoretically lower it, but don't bother since it's not required.  Fixes
various piglit image load/store tests.

Suggested-by: Ilia Mirkin <imirkin@alum.mit.edu>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/13852>

src/gallium/drivers/freedreno/a5xx/fd5_screen.c

@@ -90,6 +90,11 @@ fd5_screen_is_format_supported(struct pipe_screen *pscreen,
                          PIPE_BIND_COMPUTE_RESOURCE);
    }
 
+   if (usage & PIPE_BIND_SHADER_IMAGE) {
+      if (sample_count > 1)
+         return false;
+   }
+
    /* For ARB_framebuffer_no_attachments: */
    if ((usage & PIPE_BIND_RENDER_TARGET) && (format == PIPE_FORMAT_NONE)) {
       retval |= usage & PIPE_BIND_RENDER_TARGET;

src/gallium/drivers/freedreno/a6xx/fd6_screen.c

@@ -89,6 +89,11 @@ fd6_screen_is_format_supported(struct pipe_screen *pscreen,
       retval |= usage & (PIPE_BIND_SAMPLER_VIEW | PIPE_BIND_SHADER_IMAGE);
    }
 
+   if (usage & PIPE_BIND_SHADER_IMAGE) {
+      if (sample_count > 1)
+         return false;
+   }
+
    if ((usage &
         (PIPE_BIND_RENDER_TARGET | PIPE_BIND_DISPLAY_TARGET |
          PIPE_BIND_SCANOUT | PIPE_BIND_SHARED | PIPE_BIND_COMPUTE_RESOURCE)) &&