ASoC: Reintroduce do_spi_write()

There is an unfortunate difference in return values between spi_write()
and i2c_master_send() so we need an adaptor function to translate.

Reported-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Acked-by: Liam Girdwood <lrg@ti.com>