dmaengine: ste_dma40: Add missing IRQ check in d40_probe

[ Upstream commit c05ce690 ]

Check for the return value of platform_get_irq(): if no interrupt
is specified, it wouldn't make sense to call request_irq().

Fixes: 8d318a50

 ("DMAENGINE: Support for ST-Ericssons DMA40 block v3")
Signed-off-by: Ruan Jinjie <ruanjinjie@huawei.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20230724144108.2582917-1-ruanjinjie@huawei.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>