spi: fsl-espi: fix handling of word sizes other than 8 bit

spi: fsl-espi: fix handling of word sizes other than 8 bit

The code in fsl_espi_tx_buf_lsb and parts of fsl_espi_setup_transfer
look very weird and don't reflect the ESPI spec.
ESPI stores values with <= 8 bit word size right justified as 8 bit
value and values with > 8 bit word size right justified as 16 bit
value. Therefore no such shifting is needed.
Only case MSB-first with 8 bit word size is correctly handled,
and most likely nobody ever used this driver with a different config.

On ESPI only the case LSB-first with word size > 8 bit needs a
special handling. In this case a little endian 16 bit value has
to be written to the TX FIFO what requires a byte swap as the
host system is big endian.
The same applies to reading from the RX FIFO.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: Mark Brown <broonie@kernel.org>