This fixes PLL being unable to lock, and is derived from an equivalent
downstream commit.

Available LT9611 documentation does not list this register, neither does
LT9611UXC (which is a different chip).

This commit has been confirmed to fix HDMI output on DragonBoard 845c.

Suggested-by: Amit Pundir <amit.pundir@linaro.org>
Reviewed-by: Amit Pundir <amit.pundir@linaro.org>
Signed-off-by: Robert Foss <robert.foss@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20221213150304.4189760-1-robert.foss@linaro.org