ARM: s3c24xx: move spi fiq handler into platform

The fiq handler needs access to some register definitions that
should not be used directly by device drivers.

Since this is closely related to the irqchip driver anyway,
move it into the same place.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
[krzk: Add a header guard in include/linux/spi/s3c24xx-fiq.h, fix
       SPDX comment style, update maintainer's entry]
Co-developed-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Link: https://lore.kernel.org/r/20200806182059.2431-23-krzk%40kernel.org


Acked-by: Mark Brown <broonie@kernel.org>