clk: ppc-corenet: Fix Section mismatch warning

WARNING: drivers/built-in.o(.data+0x10258):
Section mismatch in reference from the variable ppc_corenet_clk_driver
to the (unknown reference) .init.rodata:(unknown)
The variable ppc_corenet_clk_driver references
the (unknown reference) __initconst (unknown)
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

Signed-off-by: Jingchang Lu <jingchang.lu@freescale.com>
Signed-off-by: Mike Turquette <mturquette@linaro.org>