wl1271_sdio_test: Add module for sdio RX/TX testing

This module enables individually generating RX and TX traffic
over the SDIO bus on which the WL1271 chipset is connected.
This is required to perform RF interference testing.

The module takes 2 module parameters 'rx' and 'tx'.

To generate RX traffic:
	modprobe wl1271_sdio_test rx=1
To generate TX traffic:
	modprobe wl1271_sdio_test tx=1

To generate both RX & TX traffic, set both rx and tx to 1.

You can change the testing configuration at runtime by changing
the rx & tx values at /sys/modules/wl1271_sdio_test/

To stop testing simply unload the module.

Signed-off-by: Roger Quadros <roger.quadros@nokia.com>
Reviewed-by: Carlos Chinea <carlos.chinea@nokia.com>
Signed-off-by: Luciano Coelho <luciano.coelho@nokia.com>