vga_switcheroo: Fix missing gpu_bound call at audio client registration

The commit 37a3a98ef601 ("ALSA: hda - Enable runtime PM only for
discrete GPU") added a new ops gpu_bound to be called when GPU gets
bound. The patch overlooked, however, that vga_switcheroo_enable() is
called only once at GPU is bound. When an audio client is registered
after that point, it would miss the gpu_bound call. This leads to the
unexpected lack of runtime PM in HD-audio side.

For addressing that regression, just call gpu_bound callback manually
at vga_switcheroo_register_audio_client() when the GPU was already
bound.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=201615
Fixes: 37a3a98ef601 ("ALSA: hda - Enable runtime PM only for discrete GPU")
Cc: <[e-mail]>
Reviewed-by: Lukas Wunner <[e-mail]>
Signed-off-by: Takashi Iwai <[e-mail]>

drivers/gpu/vga/vga_switcheroo.c

···
 			mutex_unlock(&vgasr_mutex);
 			return -EINVAL;
 		}
+		/* notify if GPU has been already bound */
+		if (ops->gpu_bound)
+			ops->gpu_bound(pdev, id);
 	}
 	mutex_unlock(&vgasr_mutex);