spi: sh-hspi: Remove duplicate code to set default transfer speed

In the implementation of __spi_validate(), spi core will use spi device's max
speed as default transfer speed if it is not set for this transfer.
So we can remove the same logic in hspi_hw_setup().

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Mark Brown <broonie@linaro.org>