mensactrl: Add a blank 8th row so we don't duplicate the 7th

vblank can not be disabled and if we don't clear the shift registers
before their content will bleed into the first row.

src/mensactrl.c

@@ -123,7 +123,7 @@ static struct mensa_fb *setup_fb(const char *devname, int hmodules, int vmodules
 	}
 	memset(mensafb->inputfb, 0, mensafb->x_res * mensafb->y_res);
 
-	mensafb->fbmem=mmap(NULL, mensafb->size * 2,
+	mensafb->fbmem=mmap(NULL, mensafb->size * 2 + mensafb->x_res * LINES_PER_MODULE * 2,
 			PROT_READ|PROT_WRITE, MAP_SHARED, mensafb->fd, 0);
 	if (mensafb->fbmem==NULL) {
 		perror("mmap'ing fb");
@@ -131,7 +131,7 @@ static struct mensa_fb *setup_fb(const char *devname, int hmodules, int vmodules
 		free(mensafb);
 		exit(1);
 	}
-	for (i = 0; i < mensafb->size ; i++)
+	for (i = 0; i < mensafb->size + mensafb->x_res * LINES_PER_MODULE; i++)
 		mensafb->fbmem[i] = ((6 + i / (mensafb->x_res * LINES_PER_MODULE)) % 7)<<5;
 
 	mensafb->hmodules = hmodules;