drm: vc4: Fix possible null pointer dereference

In vc4_hdmi_audio_init() of_get_address() may return
NULL which is later dereferenced. Fix this bug by adding NULL check.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: bb7d7856 ("drm/vc4: Add HDMI audio support")
Signed-off-by: Aleksandr Mishin <amishin@t-argos.ru>
Signed-off-by: Maxime Ripard <mripard@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20240409075622.11783-1-amishin@t-argos.ru

drivers/gpu/drm/vc4/vc4_hdmi.c

@@ -2740,6 +2740,8 @@ static int vc4_hdmi_audio_init(struct vc4_hdmi *vc4_hdmi)
 		index = 1;
 
 	addr = of_get_address(dev->of_node, index, NULL, NULL);
+	if (!addr)
+		return -EINVAL;
 
 	vc4_hdmi->audio.dma_data.addr = be32_to_cpup(addr) + mai_data->offset;
 	vc4_hdmi->audio.dma_data.addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;