wireless: Remove redundant spi driver bus initialization

In ancient times it was necessary to manually initialize the bus field of an
spi_driver to spi_bus_type. These days this is done in spi_driver_register(),
so we can drop the manual assignment.

The patch was generated using the following coccinelle semantic patch:
// <smpl>
@@
identifier _driver;
@@
struct spi_driver _driver = {
.driver = {
- .bus = &spi_bus_type,
},
};
// </smpl>

Signed-off-by: Lars-Peter Clausen <[e-mail]>
Cc: Dan Williams <[e-mail]>
Cc: "John W. Linville" <[e-mail]>
Cc: Christian Lamparter <[e-mail]>
Cc: Luciano Coelho <[e-mail]>
Cc: [e-mail]
Cc: [e-mail]
Acked-by: Luciano Coelho <[e-mail]>
Signed-off-by: John W. Linville <[e-mail]>

drivers/net/wireless/libertas/if_spi.c

···
 	.remove = __devexit_p(libertas_spi_remove),
 	.driver = {
 		.name	= "libertas_spi",
-		.bus	= &spi_bus_type,
 		.owner	= THIS_MODULE,
 		.pm	= &if_spi_pm_ops,
 	},

drivers/net/wireless/p54/p54spi.c

···
 static struct spi_driver p54spi_driver = {
 	.driver = {
 		.name		= "p54spi",
-		.bus		= &spi_bus_type,
 		.owner		= THIS_MODULE,
 	},
 

drivers/net/wireless/wl1251/spi.c

···
 static struct spi_driver wl1251_spi_driver = {
 	.driver = {
 		.name		= DRIVER_NAME,
-		.bus		= &spi_bus_type,
 		.owner		= THIS_MODULE,
 	},
 

drivers/net/wireless/wl12xx/spi.c

···
 static struct spi_driver wl1271_spi_driver = {
 	.driver = {
 		.name		= "wl1271_spi",
-		.bus		= &spi_bus_type,
 		.owner		= THIS_MODULE,
 	},