ARM: OMAP1: Remove omap_sram_idle()

This patch removes omap_sram_idle() that is no longer used.

The function called in pm_idle is omap_sram_suspend, omap_sram_idle() is
not used anywhere in omap1.

Signed-off-by: Vivek Kutal <vivek.kutal@celunite.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>