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.c

@@ -936,6 +936,8 @@ struct spi_master *spi_alloc_master(struct device *dev, unsigned size)
 		return NULL;
 
 	device_initialize(&master->dev);
+	master->bus_num = -1;
+	master->num_chipselect = 1;
 	master->dev.class = &spi_master_class;
 	master->dev.parent = get_device(dev);
 	spi_master_set_devdata(master, &master[1]);