cpuidle, OMAP3: Use WFI for omap3_pm_idle()

arch_cpu_idle() is a very simple idle interface and exposes only a
single idle state and is expected to not require RCU and not do any
tracing/instrumentation.

As such, omap_sram_idle() is not a valid implementation. Replace it
with the simple (shallow) omap3_do_wfi() call. Leaving the more
complicated idle states for the cpuidle driver.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Tony Lindgren <tony@atomide.com>
Tested-by: Ulf Hansson <ulf.hansson@linaro.org>
Acked-by: Tony Lindgren <tony@atomide.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Frederic Weisbecker <frederic@kernel.org>
Link: https://lore.kernel.org/r/20230112195541.538053457@infradead.org

arch/arm/mach-omap2/pm34xx.c

@@ -294,7 +294,7 @@ static void omap3_pm_idle(void)
 	if (omap_irq_pending())
 		return;
 
-	omap_sram_idle();
+	omap3_do_wfi();
 }
 
 #ifdef CONFIG_SUSPEND