macfb: fix VRAM dirty memory region logging

macfb: fix VRAM dirty memory region logging

The macfb VRAM memory region was configured with coalescing rather than dirty
memory logging enabled, causing some areas of the screen not to redraw after
a full screen update.

Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Fixes: 8ac919a065 ("hw/m68k: add Nubus macfb video card")
Reviewed-by: Laurent Vivier <laurent@vivier.eu>
Message-Id: <20220108164147.30813-1-mark.cave-ayland@ilande.co.uk>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>