clk: Make clk API return per-user struct clk instances

clk: Make clk API return per-user struct clk instances

Moves clock state to struct clk_core, but takes care to change as little API as
possible.

struct clk_hw still has a pointer to a struct clk, which is the
implementation's per-user clk instance, for backwards compatibility.

The struct clk that clk_get_parent() returns isn't owned by the caller, but by
the clock implementation, so the former shouldn't call clk_put() on it.

Because some boards in mach-omap2 still register clocks statically, their clock
registration had to be updated to take into account that the clock information
is stored in struct clk_core now.

Signed-off-by: Tomeu Vizoso <[email protected]>
Reviewed-by: Stephen Boyd <[email protected]>
Tested-by: Tony Lindgren <[email protected]>
Signed-off-by: Michael Turquette <[email protected]>
[[email protected]: adapted clk_has_parent to struct clk_core
                        applied OMAP3+ DPLL fix from Tero & Tony]