video: Use fractional units for X coordinates

With anti-aliased fonts we need a more fine-grained horizontal position
than a single pixel. Characters can be positioned to start part-way through
a pixel, with anti-aliasing (greyscale edges) taking care of the visual
effect.

To cope with this, use fractional units (1/256 pixel) for horizontal
positions in the text console.

Signed-off-by: Simon Glass <sjg@chromium.org>
[agust: rebased]
Signed-off-by: Anatolij Gustschin <agust@denx.de>
diff --git a/test/dm/video.c b/test/dm/video.c
index 9f5e7fc..be94633 100644
--- a/test/dm/video.c
+++ b/test/dm/video.c
@@ -106,14 +106,14 @@
 	ut_asserteq(46, compress_frame_buffer(dev));
 
 	for (i = 0; i < 20; i++)
-		vidconsole_putc_xy(con, i * 8, 0, ' ' + i);
+		vidconsole_putc_xy(con, VID_TO_POS(i * 8), 0, ' ' + i);
 	ut_asserteq(273, compress_frame_buffer(dev));
 
 	vidconsole_set_row(con, 0, WHITE);
 	ut_asserteq(46, compress_frame_buffer(dev));
 
 	for (i = 0; i < 20; i++)
-		vidconsole_putc_xy(con, i * 8, 0, ' ' + i);
+		vidconsole_putc_xy(con, VID_TO_POS(i * 8), 0, ' ' + i);
 	ut_asserteq(273, compress_frame_buffer(dev));
 
 	return 0;