spi: fsi: Make available for build test

There is no build time dependency on the platform support so add an
|| COMPILE_TEST so we've got better build coverage of the driver.

Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20230221-spi-arch-deps-v1-5-83d1566474cf@kernel.org


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