clk: keystone: syscon-clk: Add support for AM64 specific epwm-tbclk

AM64 has 9 instances of EPWM modules. And each instance has a clk to
Timer-Base sub-module that can be controlled by Control module. Update
the driver with all the 9 instance of clocks associated to
ti,am64-epwm-tbclk.

Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
Link: https://lore.kernel.org/r/20210528045743.16537-3-lokeshvutla@ti.com


Reviewed-by: Tero Kristo <kristo@kernel.org>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>