media: nuvoton: VIDEO_NPCM_VCD_ECE should depend on ARCH_NPCM

The Nuvoton NPCM Video Capture/Differentiation Engine (VCD) and Encoding
Compression Engine (ECE) are only present on Nuvoton NPCM SoCs.  Hence
add a dependency on ARCH_NPCM, to prevent asking the user about these
drivers when configuring a kernel without  Nuvoton NPCM Architecture
support.

Fixes: 46c15a4f ("media: nuvoton: Add driver for NPCM video capture and encoding engine")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>