OMAP: PM debug: fix section mismatch warnings

WARNING: arch/arm/mach-omap2/built-in.o(.text+0x423c): Section mismatch in reference from the function pm_dbg_regset_init() to the function .init.text:pm_dbg_init()
The function pm_dbg_regset_init() references
the function __init pm_dbg_init().
This is often because pm_dbg_regset_init lacks a __init
annotation or the annotation of pm_dbg_init is wrong.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Kevin Hilman <khilman@ti.com>