arm64: dts: rockchip: Do not enable hdmi_sound node on Pinebook Pro

Remove the redundant enabling of the hdmi_sound node in the Pinebook Pro
board dts file, because the HDMI output is unused on this device. [1][2]

This change also eliminates the following kernel log warning, which is
caused by the unenabled dependent node of hdmi_sound that ultimately
results in the node's probe failure:

platform hdmi-sound: deferred probe pending: asoc-simple-card: parse error

[1] https://files.pine64.org/doc/PinebookPro/pinebookpro_v2.1_mainboard_schematic.pdf
[2] https://files.pine64.org/doc/PinebookPro/pinebookpro_schematic_v21a_20220419.pdf

Cc: stable@vger.kernel.org
Fixes: 5a65505a69884 ("arm64: dts: rockchip: Add initial support for Pinebook Pro")
Signed-off-by: Jun Yan <jerrysteve1101@gmail.com>
Reviewed-by: Peter Robinson <pbrobinson@gmail.com>
Reviewed-by: Dragan Simic <dsimic@manjaro.org>
Link: https://patch.msgid.link/20260116151253.9223-1-jerrysteve1101@gmail.com
Signed-off-by: Heiko Stuebner <heiko@sntech.de>