spi: stm32: finalize message either on dma callback or EOT

Depending on the usage, it is necessary to perform the finalize
message operation either upon receiving the EOT interruption,
eiher upon receiving the DMA callback. Indeed, when relying
on DMA, even if the SPI EOT IT has been received, it is
necessary to wait for the end of the DMA RX transaction before
accessing to the data.

Signed-off-by: Alain Volmat <alain.volmat@foss.st.com>
Link: https://lore.kernel.org/r/1625646426-5826-8-git-send-email-alain.volmat@foss.st.com


Signed-off-by: Mark Brown <broonie@kernel.org>