of/spi: mpc512x_psc_spi.c: Fix build failures

Fixes build errors caused by the:
 - OF device_node pointer being moved into struct device
 - removal of the match_table field from struct of_platform_driver

Signed-off-by: Anatolij Gustschin <agust@denx.de>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>