ARM: OMAP2+: PM: fix section mismatch with omap2_init_processor_devices()

Fix the below warning by making omap2_init_processor_devices() __init.
It is called by an __init function and calls only __init functions, so
it should also be init.

WARNING: arch/arm/mach-omap2/built-in.o(.text+0x183c): Section mismatch in reference from the function omap2_init_processor_devices() to the function .init.text:_init_omap_device()
The function omap2_init_processor_devices() references
the function __init _init_omap_device().
This is often because omap2_init_processor_devices lacks a __init
annotation or the annotation of _init_omap_device is wrong.
Reported-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Kevin Hilman <khilman@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>

arch/arm/mach-omap2/pm.c

@@ -49,7 +49,7 @@ static int _init_omap_device(char *name)
 /*
  * Build omap_devices for processors and bus.
  */
-static void omap2_init_processor_devices(void)
+static void __init omap2_init_processor_devices(void)
 {
 	_init_omap_device("mpu");
 	if (omap3_has_iva())