dmaengine: stm32: Simplify with dev_err_probe()

Common pattern of handling deferred probe can be simplified with
dev_err_probe().  Less code and the error value gets printed.

Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Link: https://lore.kernel.org/r/20200828152637.16903-2-krzk@kernel.org


Signed-off-by: Vinod Koul <vkoul@kernel.org>