spi: bcm2835: Replace spi_master by spi_controller

Commit 8caab75f ('spi: Generalize SPI "master" to "controller"')
changed the "spi_master" nomenclature to "spi_controller", necessitating
a conversion of all drivers.

Perform this conversion for the BCM2835 SPI driver.
No functional change intended.
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Cc: Frank Pavlic <f.pavlic@kunbus.de>
Cc: Martin Sperl <kernel@martin.sperl.org>
Cc: Noralf Trønnes <noralf@tronnes.org>
Cc: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Mark Brown <broonie@kernel.org>