[poppler] splashModeDeviceN8 in two switch

[Albert Astals Cid]

This is mostly for William since AFAIK he's the "only" one using SPLASH_CMYK.

I've tried to enable SPLASH_CMYK on the CI and it's loudly complaining that the splashModeDeviceN8 cases are missing in SplashOutputDev.cc

https://gitlab.freedesktop.org/aacid/poppler/-/jobs/253647

Any suggestion of what the code should be?

Should they just be the same as case splashModeCMYK8: ? The first one looks like it may make sense, but not so sure about the second.

Cheers,
  Albert