clk: ti: add support for clkctrl clocks

Previously, hwmod core has been used for controlling the hwmod level
clocks directly. This has certain drawbacks, like being unable to share
the clocks for multiple users, missing usecounting and generally being
totally incompatible with the common clock framework.

This patch adds support for clkctrl clocks for addressing the above
issues. These support the modulemode handling, which will replace the
direct hwmod clkctrl linkage. Any optional clocks are also supported,
gate, mux and divider.

Signed-off-by: Tero Kristo <t-kristo@ti.com>
Acked-by: Tony Lindgren <tony@atomide.com>