powerpc/cpm: Remove SPI defines and spi structs

When cpm2.h included into spi_mpc8xxx driver, the SPI defines
in the header conflict with defines in the driver.

We don't need them in the header file, so remove them. Plus
remove "struct spi", we'll use a better version in the driver.

Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>