spi/spi-atmel: add flag to controller data for lock operations

Will allow to drop the lock during DMA operations.

Replacing non-irqsave versions with irqsave versions of the lock
to make it correct in both pdc and dmaengine transfer mode

Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
[wenyou.yang@atmel.com: submit the patch]
Signed-off-by: Wenyou Yang <wenyou.yang@atmel.com>
Tested-by: Richard Genoud <richard.genoud@gmail.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>