PCI: PM: Do not call platform_pci_power_manageable() unnecessarily

Drop two invocations of platform_pci_power_manageable() that are not
necessary, because the functions called when it returns 'true' do the
requisite "power manageable" checks themselves.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Ferry Toth <fntoth@gmail.com>