Build failure if CONFIG_DRM_VC4_HDMI_CEC is disabled (trivial patch included)

[asavah]

Describe the bug
If VC4_HDMI_CEC is disabled in kernel config build fails
Edit: using branch rpi-5.10.y

To reproduce
Build the kernel with aforementioned option disabled

Expected behaviour
Clean build

Actual behaviour

grep VC4_HDMI_CEC .config
# CONFIG_DRM_VC4_HDMI_CEC is not set

drivers/gpu/drm/vc4/vc4_hdmi.c: In function ‘vc4_hdmi_cec_resume’:
drivers/gpu/drm/vc4/vc4_hdmi.c:2333:16: error: ‘return’ with a value, in function returning void [-Werror=return-type]
 2333 |         return 0;
      |                ^
drivers/gpu/drm/vc4/vc4_hdmi.c:2331:13: note: declared here
 2331 | static void vc4_hdmi_cec_resume(struct vc4_hdmi *vc4_hdmi)
      |             ^~~~~~~~~~~~~~~~~~~
drivers/gpu/drm/vc4/vc4_hdmi.c: In function ‘vc4_hdmi_runtime_resume’:
drivers/gpu/drm/vc4/vc4_hdmi.c:2573:13: error: void value not ignored as it ought to be
 2573 |         ret = vc4_hdmi_cec_resume(vc4_hdmi);
      |             ^
cc1: some warnings being treated as errors

Patch:

diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c
index 6aa074714305..b621fc3b1750 100644
--- a/drivers/gpu/drm/vc4/vc4_hdmi.c
+++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
@@ -2328,7 +2328,7 @@ static int vc4_hdmi_cec_init(struct vc4_hdmi *vc4_hdmi)
 
 static void vc4_hdmi_cec_exit(struct vc4_hdmi *vc4_hdmi) {};
 
-static void vc4_hdmi_cec_resume(struct vc4_hdmi *vc4_hdmi)
+static int vc4_hdmi_cec_resume(struct vc4_hdmi *vc4_hdmi)
 {
 	return 0;
 }

[pelwell]

Thanks!