phy: rockchip: samsung-hdptx: Add HDMI 2.1 FRL support

The PHY is capable of handling four HDMI 2.1 Fixed Rate Link (FRL)
lanes, and each one can operate at any of the rates of 3Gbps, 6Gbps,
8Gbps, 10Gbps or 12Gbps.

Add the necessary driver changes to support the feature.

Co-developed-by: Algea Cao <algea.cao@rock-chips.com>
Signed-off-by: Algea Cao <algea.cao@rock-chips.com>
Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@collabora.com>
Link: https://patch.msgid.link/20260113-phy-hdptx-frl-v6-11-8d5f97419c0b@collabora.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>

Author: cristicc