media: pci: mgb4: add COMMON_CLK dependency

This driver fails to build when HAVE_CLK and COMMON_CLK are disabled:

x86_64-linux-ld: vmlinux.o: in function `mgb4_remove':
mgb4_core.c:(.text+0x1915e8c): undefined reference to `clkdev_drop'
x86_64-linux-ld: mgb4_core.c:(.text+0x1915e98): undefined reference to `clk_hw_unregister'

Add a Kconfig dependency to enforce a clean build.

Fixes: 0ab13674a9bd ("media: pci: mgb4: Added Digiteq Automotive MGB4 driver")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Martin Tůma <martin.tuma@digiteqautomotive.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>

media: pci: mgb4: Added Digiteq Automotive MGB4 driver

Digiteq Automotive MGB4 is a modular frame grabber PCIe card for automotive
video interfaces. As for now, two modules - FPD-Link and GMSL - are
available and supported by the driver. The card has two inputs and two
outputs (FPD-Link only).

In addition to the video interfaces it also provides a trigger signal
interface and a MTD interface for FPGA firmware upload.

Signed-off-by: Martin Tůma <martin.tuma@digiteqautomotive.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>