clk: ppc-corenet: fix section mismatch warning

In order to fix the following section mismatch warning:
  WARNING: drivers/clk/built-in.o(.data+0xe4): Section mismatch in reference from the variable ppc_corenet_clk_driver to the function .init.text:ppc_corenet_clk_probe()
  The variable ppc_corenet_clk_driver references
  the function __init ppc_corenet_clk_probe()
  If the reference is valid then annotate the
  variable with __init* or __refdata (see linux/init.h) or name the variable:
  *_template, *_timer, *_sht, *_ops, *_probe, *_probe_one, *_console

  WARNING: drivers/clk/built-in.o(.data+0x10c): Section mismatch in reference from the variable ppc_corenet_clk_driver to the variable .init.rodata:ppc_clk_ids
  The variable ppc_corenet_clk_driver references
  the variable __initconst ppc_clk_ids
  If the reference is valid then annotate the
  variable with __init* or __refdata (see linux/init.h) or name the variable:
  *_template, *_timer, *_sht, *_ops, *_probe, *_probe_one, *_console

We can't just add the __init annotation to ppc_corenet_clk_driver or
remove the __init from ppc_corenet_clk_probe() and ppc_clk_ids.
So choose to use CLK_OF_DECLARE to scan and init the clock devices.

Signed-off-by: Kevin Hao <haokexin@gmail.com>
Acked-by: Scott Wood <scottwood@freescale.com>
Acked-by: Michael Turquette <mturquette@linaro.org>
Signed-off-by: Michael Turquette <mturquette@linaro.org>