dmaengine: idxd: Fix missing error code in idxd_cdev_open()

The error code is missing in this code scenario, add the error code
'-EINVAL' to the return value 'rc'.

Eliminate the follow smatch warning:

drivers/dma/idxd/cdev.c:113 idxd_cdev_open() warn: missing error code
'rc'.

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Acked-by: Dave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/1622628446-87909-1-git-send-email-jiapeng.chong@linux.alibaba.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>