WLAN and SPI: direct interrupt

[Werner Almesberger]

I wrote:
>	 			Throughput at receiver	System time
> SDIO interrupt polling:	386.1 kB/s      (100%)	3.5s	(100%)
> Direct card interrupt:	402.6 kB/s      (104%)	2.9s	( 83%)
> Asynchronous HIF:		448.8 kB/s      (116%)	2.5s 	( 71%)

For comparison:

Atheros stack, Openmoko mainline:	707.0 kB/s
My laptop (Fujitsu U1010, AR5006EG):	2300-2900 kB/s (high variance)

- Werner