spi: davinci: Initialize dspi->done before any possible use of it

On SOC with multiple cpu (like omal l138) it is possible that spi
periferic is already initialized when this module is loaded and so
it is possible to recieve interrupt when the modules is not fully
initialized.

this patch initialize dspi->done before refister the interrupt
handler that use it

Signed-off-by: Michele Dionisio <michele.dionisio@gmail.com>
Signed-off-by: Mark Brown <broonie@kernel.org>