mtplot.c: Default DISPLAY of :0

Also, helpful command to turn off frame buffer compression, which
breaks mtplot on Intel.

BUG=chromium:341496
TEST=Manually tested w/ DISPLAY unset, set to :0, and set to :1.
Saw mtplot work when unset and set to :0, but fail when set to :1
Also, copied and pasted the framebuffer command to get that to work.

Change-Id: Ie50c7004296e8414e332a5da717968e9370a3c87
Reviewed-on: https://chromium-review.googlesource.com/185126
Reviewed-by: Dennis Kempin <denniskempin@chromium.org>
Commit-Queue: Andrew de los Reyes <adlr@chromium.org>
Tested-by: Andrew de los Reyes <adlr@chromium.org>
1 file changed