Revert "framebuffer: reset VTG"

This reverts commit 6cb18f5ce3c9c63250cfbe738b84ec7beb1a9412.

Conflicts:
	misoclib/framebuffer/__init__.py
	misoclib/framebuffer/format.py
videomixer: select 1024x768 by default
framebuffer: fix resynchronization after resolution change