spi: spi-cadence-quadspi: Revert "Fix division by zero warning"

Revert to change to a better code.

This reverts commit 55cef88b.

Signed-off-by: Yoshitaka Ikeda <ikeda@nskint.co.jp>
Link: https://lore.kernel.org/r/bd30bdb4-07c4-f713-5648-01c898d51f1b@nskint.co.jp


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