[PATCH] ARM: OMAP: omap2_mcspi: use the per transfer wordsize and speed overrides

Each transfer in an SPI message can have its wordsize and speed override.
Add a omap2_mcspi_setup_transfer to handle this.

Interpret spi->bits_per_word == 0 as a default wordsize of 8.

Signed-off-by: Imre Deak <imre.deak@nokia.com>