clk: ti: dm816: enable sysclk6_ck on init

We need sysclk6_ck enabled early as it is needed by l4_ls and system
timers early on boot. This removes the dependency of system timers to
the interconnect related code that can be then probed later on when
suitable at module_init time.

Cc: linux-clk@vger.kernel.org
Cc: Grygorii Strashko <grygorii.strashko@ti.com>
Cc: Michael Turquette <mturquette@baylibre.com>
Cc: Rob Herring <robh@kernel.org>
Cc: Stephen Boyd <sboyd@kernel.org>
Cc: Tero Kristo <t-kristo@ti.com>
Acked-by: Stephen Boyd <sboyd@kernel.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>