edid: Use a better mode for 640x480

The hardcoded clock value for 640x480 was 25.175 MHz.  That's a valid
clock to use, but is quite hard to make a non-jittery clock from PLLs.
It's much easier to make 25.200 MHz, so let's do that.

The difference between the two modes is 59.9 Hz vs. 60 Hz and it seems
better to make a non-jittery 60 Hz rather than a very jittery 59.9 Hz.

BRANCH=none
BUG=chrome-os-partner:46256
TEST=Insignia monitor works, so do others

Change-Id: I8aa124d04a90f5dcf9cfa923ed3b693fbb4a06d8
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Original-Commit-Id: e32ce13462101dc60cfed60b6948b7597e93525a
Original-Change-Id: Ia9804afe8011a915e4bec306e863d34ad7e27be5
Original-Signed-off-by: Douglas Anderson <dianders@chromium.org>
Original-Reviewed-on: https://chromium-review.googlesource.com/309540
Original-Reviewed-by: Stphane Marchesin <marcheu@chromium.org>
Original-(cherry picked from commit 7f32c9f460991e5e3b947117d6ae4080e630a532)
Original-Reviewed-on: https://chromium-review.googlesource.com/309576
Original-Commit-Ready: David Hendricks <dhendrix@chromium.org>
Original-Tested-by: David Hendricks <dhendrix@chromium.org>
Original-Reviewed-by: David Hendricks <dhendrix@chromium.org>
Original-Reviewed-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: http://review.coreboot.org/12443
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

src/lib/edid.c

@@ -1003,7 +1003,7 @@ static void dump_breakdown(unsigned char *edid)
  */
 static struct edid_mode known_modes[NUM_KNOWN_MODES] = {
 	[EDID_MODE_640x480_60Hz] = {
-		.name = "640x480@60Hz", .pixel_clock = 25175, .refresh = 60,
+		.name = "640x480@60Hz", .pixel_clock = 25200, .refresh = 60,
 		.ha = 640, .hbl = 160, .hso = 16, .hspw = 96,
 		.va = 480, .vbl = 45, .vso = 10, .vspw = 2,
 		.phsync = '-', .pvsync = '-' },