dt-bindings: phy: Convert AM654 SERDES bindings to YAML

Convert SERDES dt-bindings for TI's AM654 SoC to YAML binding.

Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20210723135605.23572-1-kishon@ti.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>