spi: gpio: Follow renaming of SPI "master" to "controller"

In commit 8caab75fd2c2 ("spi: Generalize SPI "master" to "controller"")
some functions and struct members were renamed. Recent work by Uwe
completes this renaming. However, there are plenty of leftovers in
the comments and in-code documentation. Update them as well.

Signed-off-by: Andy Shevchenko <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Mark Brown <[e-mail]>

include/linux/spi/spi_gpio.h

···
  */
 
 /**
- * struct spi_gpio_platform_data - parameter for bitbanged SPI master
- * @num_chipselect: how many slaves to allow
+ * struct spi_gpio_platform_data - parameter for bitbanged SPI host controller
+ * @num_chipselect: how many target devices to allow
  */
 struct spi_gpio_platform_data {
 	u16		num_chipselect;