spi: mpc512x: Call mpc512x_psc_spi_transfer_setup() unconditionally

SPI core validates both bits_per_word and speed_hz transfer parameters and
thus the if statement here is needless as it will always call the
mpc512x_psc_spi_transfer_setup().

Signed-off-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>