T30 boot hang with CONFIG_PM_LEGACY=n

[Len Brown <len.brown@intel.com>]

My T30 doesn't boot if CONFIG_PM_LEGACY=n
unless "apm=off".

Seems that this build option causes PM_IS_ACTIVE() to be constant 0,
which disables APM's check to see if ACPI is running:

apm_init()
	...
        if (PM_IS_ACTIVE()) {
                printk(KERN_NOTICE "apm: overridden by ACPI.\n");
                apm_info.disabled = 1;
                return -ENODEV;
        }

Apparently when CONFIG_PM_LEGACY was created, CONFIG_APM depended
on it, so apm.c wasn't built.  But that dependency was later removed so it is now possible
to build APM with its check for ACPI  mysteriously disabled -- much to the unhappyness
of my T30.

What's the plan here?  Perhaps that plan should be written down
in kernel/power/Kconfig? 

config PM_LEGACY
        bool "Legacy Power Management API"
        depends on PM
        default y
        ---help---
           Support for pm_register() and friends.

           If unsure, say Y.

thanks,
-Len