ARM: OMAP2+: Block suspend for am3 and am4 if PM is not configured

If the PM related modules are not loaded and PM firmware not configured,
the system suspend fails to resume. Let's fix this by adding initial
platform_suspend_ops to block suspend and warn about missing modules.

When pm33xx and wkup_m3_ipc have been loaded and m3 coprocessor booted
with it's firmware, pm33xx sets up working platform_suspend_ops. Note
that we need to configure at least PM_SUSPEND_STANDBY to have
suspend_set_ops().

Cc: Dave Gerlach <d-gerlach@ti.com>
Cc: Suman Anna <s-anna@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>