In the Linux kernel, the following vulnerability has been resolved: drm/amd/display: Check for tg ops in dce110_set_avmute Some older DCE

In the Linux kernel, the following vulnerability has been resolved:

drm/amd/display: Check for tg ops in dce110_set_avmute

Some older DCE timing generators do not implement is_tg_enabled in
their ops table. Calling it unconditionally when waiting for AV mute
frames causes a NULL pointer dereference on Southern Islands dGPUs
when turning the display off over HDMI.

Check that tg and the required ops exist before waiting for frames.

(cherry picked from commit 2686a0c0aaa07bec2e24131835cf27b5fd4935a5)