clk: ti: change clock init to use generic of_clk_init

Previously, the TI clock driver initialized all the clocks hierarchically
under each separate clock provider node. Now, each clock that requires
IO access will instead check their parent node to find out which IO range
to use.

This patch allows the TI clock driver to use a few new features provided
by the generic of_clk_init, and also allows registration of clock nodes
outside the clock hierarchy (for example, any external clocks.)

Signed-off-by: Tero Kristo <t-kristo@ti.com>
Cc: Mike Turquette <mturquette@linaro.org>
Cc: Paul Walmsley <paul@pwsan.com>
Cc: Tony Lindgren <tony@atomide.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Peter Ujfalusi <peter.ujfalusi@ti.com>
Cc: Jyri Sarha <jsarha@ti.com>
Cc: Stefan Assmann <sassmann@kpanic.de>
Acked-by: Tony Lindgren <tony@atomide.com>