drm/nouveau/dispnv04: Remove some unused functions

Removes some functions that are not used anywhere:
nv04_display_late_takedown() nv04_display_early_init()

This was partially found by using a static code analysis program
called cppcheck.

Signed-off-by: Rickard Strandqvist <rickard_strandqvist@spectrumdigital.se>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>