arm: omap: fix section mismatch warning

WARNING: arch/arm/plat-omap/built-in.o(.data+0x6d4): Section mismatch in reference from the variable omap_driver to the function .init.text:omap_cpu_init()
The variable omap_driver references
the function __init omap_cpu_init()
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: Ming Lei <tom.leiming@gmail.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>