airo : allow supend with card without power management

Some airo card don't support power Management [1].
Don't abort suspend with those cards.

00:06.0 Network controller: AIRONET Wireless Communications PC4800 (rev 01)
        Flags: medium devsel, IRQ 17
        Memory at dffffe00 (32-bit, non-prefetchable) [size=128]
        I/O ports at d000 [size=128]
        I/O ports at cc00 [size=64]
        Kernel driver in use: airo

Signed-off-by: Matthieu CASTET <castet.matthieu@free.fr>
Signed-off-by: John W. Linville <linville@tuxdriver.com>