pybootchartgui: fix 2 SyntaxWarnings

pybootchartgui: fix 2 SyntaxWarnings

scripts/pybootchartgui/pybootchartgui/draw.py:820: SyntaxWarning: "is not" with a literal. Did you mean "!="?
  if (OPTIONS.show_pid or OPTIONS.show_all) and ipid is not 0:
scripts/pybootchartgui/pybootchartgui/draw.py:918: SyntaxWarning: "is not" with a literal. Did you mean "!="?
  if i is not 0:

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
(cherry picked from commit 8d996616f0ca57220d939a41ca9ba6d696ea2a4f)
Signed-off-by: Jose Quaresma <jose.quaresma@foundries.io>
Signed-off-by: Steve Sakoman <steve@sakoman.com>