Currently, function a3700_spi_pin_mode_set() configures the SPI transfer
mode according to the value passed as second argument. This value is
detected using the raw values from a switch case.

This commit replaces these raw values by the corresponding macro
constants in linux/spi/spi.h
Signed-off-by: NRomain Perier <romain.perier@free-electrons.com>
Signed-off-by: NMark Brown <broonie@kernel.org>