libertas: remove ps_supported flag, use fwcapinfo

Power save support depends on the firmware capabilities rather than the
card's hardware interface.  Use the FW_CAPINFO_PS bit in the firmware
capabilities mask throughout the driver in place of the redundant
ps_supported flag and don't make decisions about PS support in the
interface drivers (with the exception of a special case in the USB
driver).

V2: put the USB special case in the right place.

Signed-off-by: Andrey Yurovsky <andrey@cozybit.com>
Acked-by: Dan Williams <dcbw@redhat.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/libertas/if_spi.c

@@ -1118,7 +1118,6 @@ static int __devinit if_spi_probe(struct spi_device *spi)
 	priv->card = card;
 	priv->hw_host_to_card = if_spi_host_to_card;
 	priv->fw_ready = 1;
-	priv->ps_supported = 1;
 
 	/* Initialize interrupt handling stuff. */
 	card->run_thread = 1;