Detect 1280x960 with a larger hsync counter span

Some VGA encoders end up with a hsync counter value as low as 0x3ae
for the 1280x960x60 mode. Adapt the hsync counter detection span to
handle it.

BUG=None
TEST=Test VGA frame dump with said encoders

Change-Id: Ia60eb8e752ac7950b2850b84f4558443857e00c9
Signed-off-by: Paul Kocialkowski <paul.kocialkowski@linux.intel.com>
Reviewed-on: https://chromium-review.googlesource.com/559062
Reviewed-by: Hsu Wei-Cheng <mojahsu@chromium.org>
diff --git a/chameleond/utils/rx.py b/chameleond/utils/rx.py
index d229beb..c70cd57 100644
--- a/chameleond/utils/rx.py
+++ b/chameleond/utils/rx.py
@@ -574,7 +574,7 @@
     (0x31e, 0x331, 'PC_1024x768x60'),
     (0x332, 0x352, 'PC_1280x800x60'),
     (0x3a0, 0x3a7, 'PC_1440x900x60'),
-    (0x3c0, 0x400, 'PC_1280x960x60'),
+    (0x3ad, 0x400, 'PC_1280x960x60'),
     (0x420, 0x437, 'PC_1280x1024x60'),
     (0x440, 0x459, 'PC_1680x1050x60'),
     (0x459, 0x490, 'PC_1920x1080x60'),