spi: acpi: remove superfluous parameter check

to_spi_device() already checks 'dev'. No need to do it before calling
it.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Link: https://lore.kernel.org/r/20200312134507.10000-1-wsa@the-dreams.de


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