drm/msm/hdmi: Keep the HDMI_CTRL_ENABLE bitfield always on

The ENABLE field in REG_HDMI_CTRL is required to be set to detect hot plug
events on 8x96. We don't get any HPD interrupts when HDMI bridge is
disabled.

Keep it always on. Downstream also seems to do the same thing. Restrict
this quirk only to 8x96, since we're not entirely sure whether this is
a legitimate fix or not.

Signed-off-by: Archit Taneja <architt@codeaurora.org>
Signed-off-by: Ondrej Kubik <ondrej.kubik@canonical.com>