spi: spi-geni-qcom: Simplify setup_fifo_xfer()

spi: spi-geni-qcom: Simplify setup_fifo_xfer()

The definition of SPI_FULL_DUPLEX (3) is really SPI_TX_ONLY (1) ORed
with SPI_RX_ONLY (2). Let's drop the define and simplify the code here a
bit by collapsing the setting of 'm_cmd' into conditions that are the
same.

This is a non-functional change, just cleanup to consolidate code.

Signed-off-by: Stephen Boyd <swboyd@chromium.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Link: https://lore.kernel.org/r/20200620022233.64716-2-swboyd@chromium.org
Signed-off-by: Mark Brown <broonie@kernel.org>