spi: pxa2xx: Move SSP idle waiting to cs_deassert()

Move SSP idle waiting before CS deassert from error and end of message
handling function giveback() to cs_deassert(). This ensures idle waiting
is done also if there is CS change between transfers.

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