spi: sh-msiof: Fill in spi_transfer.effective_speed_hz

Fill in the effective bit rate used for transfers, so the SPI core can
calculate instead of estimate delays.

Restore "reverse Christmas tree" order of local variables while adding
new variables.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20210113101916.1147695-2-geert+renesas@glider.be


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