drm/doc: Drop chapter "KMS Initialization and Cleanup"

It only talks about crtc, brings up intel as an example and I think is
more misleading than useful really. Plus we have lots of discussion
about how your standard kms driver should be initialized/cleaned up,
so maybe better to document this when we have a better idea.

v2: Fix typo in commit message (Nicholas).

Reviewed-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190130163006.28945-2-daniel.vetter@ffwll.ch