blacklight: 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: Richard Purdie <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

drivers/video/backlight/ams369fg06.c

···
 static struct spi_driver ams369fg06_driver = {
 	.driver = {
 		.name	= "ams369fg06",
-		.bus	= &spi_bus_type,
 		.owner	= THIS_MODULE,
 	},
 	.probe		= ams369fg06_probe,

drivers/video/backlight/ld9040.c

···
 static struct spi_driver ld9040_driver = {
 	.driver = {
 		.name	= "ld9040",
-		.bus	= &spi_bus_type,
 		.owner	= THIS_MODULE,
 	},
 	.probe		= ld9040_probe,

drivers/video/backlight/ltv350qv.c

···
 static struct spi_driver ltv350qv_driver = {
 	.driver = {
 		.name		= "ltv350qv",
-		.bus		= &spi_bus_type,
 		.owner		= THIS_MODULE,
 	},
 

drivers/video/backlight/s6e63m0.c

···
 static struct spi_driver s6e63m0_driver = {
 	.driver = {
 		.name	= "s6e63m0",
-		.bus	= &spi_bus_type,
 		.owner	= THIS_MODULE,
 	},
 	.probe		= s6e63m0_probe,