mpc52xx_psc_spi: convert to cs_control callback

mpc52xx_psc_spi driver is the last user of the legacy activate_cs and
deactivate_cs callbacks, so convert the driver to the cs_control hook and
remove the legacy callbacks from fsl_spi_platform_data struct.

Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
Cc: Grant Likely <grant.likely@secretlab.ca>
Cc: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>