spi: spi-fsl-dspi: Fix a resource leak in an error handling path

'dspi_request_dma()' should be undone by a 'dspi_release_dma()' call in the
error handling path of the probe function, as already done in the remove
function

Fixes: 90ba3703

 ("spi: spi-fsl-dspi: Add DMA support for Vybrid")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Link: https://lore.kernel.org/r/d51caaac747277a1099ba8dea07acd85435b857e.1620587472.git.christophe.jaillet@wanadoo.fr
Signed-off-by: Mark Brown <broonie@kernel.org>