spi: rspi: Merge qspi_send_pio() and qspi_receive_pio()

spi: rspi: Merge qspi_send_pio() and qspi_receive_pio()

qspi_send_pio() and qspi_receive_pio() are very similar: they both send
and receive full duplex data to/from the hardware, but ignore the data
stream in the unused direction.
Merge them into qspi_transfer_out_in(), now supporting real full duplex.

Signed-off-by: Geert Uytterhoeven <geert+renesas@linux-m68k.org>
Signed-off-by: Mark Brown <broonie@linaro.org>
(cherry picked from commit 340a15e6f0d6cd436c55693f7328a1de02fcdb96)
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>