ARM: OMAP: fix section mismatch warning for omap4_hotplug_cpu()

WARNING: arch/arm/mach-omap2/built-in.o(.text+0x8b80):
Section mismatch in reference from the function omap4_hotplug_cpu() to
the function .cpuinit.text:omap_secondary_startup()
The function omap4_hotplug_cpu() references
the function __cpuinit omap_secondary_startup().
This is often because omap4_hotplug_cpu lacks a __cpuinit
annotation or the annotation of omap_secondary_startup is wrong.

Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>