spi: By default setup spi_masters with 1 chipselect and dynamics bus number

Trivial simplification.  Instead of requiring spi master drivers to
always set the bus number (even when a dynamic number is desired),
this patch modifies spi_alloc_master() to initialize num_chipselect to
1 (because there will always be at least one CS) and bus_num to -1 for
dynamic allocation.  This simplifies the code needed to be written for
drivers.

Signed-off-by: Grant Likely <grant.likely@secretlab.ca>

drivers/spi/spi-ppc4xx.c

@@ -466,9 +466,6 @@ static int __init spi_ppc4xx_of_probe(struct platform_device *op)
 	bbp->master->setup = spi_ppc4xx_setup;
 	bbp->master->cleanup = spi_ppc4xx_cleanup;
 
-	/* Allocate bus num dynamically. */
-	bbp->master->bus_num = -1;
-
 	/* the spi->mode bits understood by this driver: */
 	bbp->master->mode_bits =
 		SPI_CPHA | SPI_CPOL | SPI_CS_HIGH | SPI_LSB_FIRST;