PCI: pci_set_power_state(): check for PM capabilities earlier

Check for PCI_CAP_ID_PM before checking the device state.  Apparently fixes
some log spam via the 3c59x driver.

Signed-off-by: Andrew Lunn <andrew.lunn@ascom.ch>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>