media: vimc: fix reference leak on failed device registration

When platform_device_register() fails in vimc_init(), the embedded
struct device in vimc_pdev has already been initialized by
device_initialize(), but the failure path returns the error without
dropping the device reference for the current platform device:

  vimc_init()
    -> platform_device_register(&vimc_pdev)
       -> device_initialize(&vimc_pdev.dev)
       -> setup_pdev_dma_masks(&vimc_pdev)
       -> platform_device_add(&vimc_pdev)

This leads to a reference leak when platform_device_register() fails.
Fix this by calling platform_device_put() before returning the error.

The issue was identified by a static analysis tool I developed and
confirmed by manual review.

Fixes: 4babf057c1 ("media: vimc: allocate vimc_device dynamically")
Cc: stable@vger.kernel.org
Signed-off-by: Guangshuo Li <lgs201920130244@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>

drivers/media/test-drivers/vimc/vimc-core.c

@@ -421,6 +421,7 @@ static int __init vimc_init(void)
 	if (ret) {
 		dev_err(&vimc_pdev.dev,
 			"platform device registration failed (err=%d)\n", ret);
+		platform_device_put(&vimc_pdev);
 		return ret;
 	}