Fix two long-standing line wrapping bugs in VGA renderer for pixel mode.

Font size may be smaller than 16 and logical scan line may be larger than
the displayed scan line.

MFC after:	3 days

sys/dev/syscons/scvgarndr.c

@@ -766,8 +766,9 @@ vga_vgadraw_direct(scr_stat *scp, int from, int count, int flip)
 		d += 8 * pixel_size;
 
 		if ((i % scp->xsize) == scp->xsize - 1)
-			d += scp->xoff * 16 * pixel_size +
-			     (scp->font_size - 1) * line_width;
+			d += scp->xoff * scp->font_size * pixel_size +
+			    scp->font_size * line_width -
+			    scp->xpixel * pixel_size;
 	}
 }