ARM: omap2: remove unused omap2_pm_init

The omap2420_init_late() and omap2430_init_late() functions
are never called. Removing them also shows that the entire
arch/arm/mach-omap2/pm24xx.c file is unused and can be
removed.

Acked-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>