ACPI: call acpi_power_init() explicitly rather than as initcall

This patch makes acpi_init() call acpi_power_init() directly.
Previously, both were subsys_initcalls.  acpi_power_init()
must happen after acpi_init(), and it's better to call it
explicitly rather than rely on link ordering.

Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
CC: Zhao Yakui <yakui.zhao@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>