uboot-imx

dm: pci: Add a 'fall through' comment

For this class it is intended to set up the PCI device, so add a comment to
indicate this. This avoids a coverity warning.

Reported-by: Coverity (CID: 134194)
Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Tom Rini <trini@konsulko.com>