m68k: drop unused parts of 68VZ328 Makefile

DRAGEN2 should obviously be CONFIG_DRAGEN2, but the screen.h entry it
triggers only references files that are nowhere to be found in the
current tree. Besides, nothing uses screen.h. So just drop all that.

Signed-off-by: Paul Bolle <pebolle@tiscali.nl>
Signed-off-by: Greg Ungerer <gerg@uclinux.org>