Description: drm/mediatek: hdmi: Perform NULL pointer check for mtk_hdmi_conf
References:
Notes:
 carnil> Introduced in 41ca9caaae0b ("drm/mediatek: hdmi: Add check for CEA modes only")
 carnil> c91026a938c2 ("drm/mediatek: hdmi: Add optional limit on maximal HDMI mode
 carnil> clock"). Vulnerable versions: 5.14-rc1.
Bugs:
upstream: released (5.16-rc7) [3b8e19a0aa3933a785be9f1541afd8d398c4ec69]
6.7-upstream-stable: N/A "Fixed before branching point"
6.6-upstream-stable: N/A "Fixed before branching point"
6.1-upstream-stable: N/A "Fixed before branching point"
5.10-upstream-stable: N/A "Vulnerable code not present"
4.19-upstream-stable: N/A "Vulnerable code not present"
sid: released (5.15.15-1)
6.1-bookworm-security: N/A "Fixed before branching point"
5.10-bullseye-security: N/A "Vulnerable code not present"
4.19-buster-security: N/A "Vulnerable code not present"