arm64: dts: ti: k3-am65*: Use generic clock for syscon clock names

serdes and ehrpwm_tbclk nodes should be using clock@ naming for nodes
following standard conventions of device tree (section 2.2.2 Generic
Names recommendation in [1]).

[1] https://github.com/devicetree-org/devicetree-specification/tree/v0.3



Suggested-by: Suman Anna <s-anna@ti.com>
Signed-off-by: Nishanth Menon <nm@ti.com>
Reviewed-by: Lokesh Vutla <lokeshvutla@ti.com>
Acked-by: Suman Anna <s-anna@ti.com>
Acked-by: Vignesh Raghavendra <vigneshr@ti.com>
Link: https://lore.kernel.org/r/20200903130015.21361-5-nm@ti.com