hw/display/artist: Remove dead code (CID 1419388 & 1419389)

hw/display/artist: Remove dead code (CID 1419388 & 1419389)

Coverity reports:

  *** CID 1419388:  Control flow issues  (DEADCODE)
  /hw/display/artist.c: 739 in draw_line_xy()
  733         if (endy < 0) {
  734             endy = 0;
  735         }
  736
  737
  738         if (endx < 0) {
  >>>     CID 1419388:  Control flow issues  (DEADCODE)
  >>>     Execution cannot reach this statement: "return;".
  739             return;
  740         }
  741
  742         if (endy < 0) {
  743             return;
  744         }

  *** CID 1419389:  Control flow issues  (DEADCODE)
  /hw/display/artist.c: 743 in draw_line_xy()
  737
  738         if (endx < 0) {
  739             return;
  740         }
  741
  742         if (endy < 0) {
  >>>     CID 1419389:  Control flow issues  (DEADCODE)
  >>>     Execution cannot reach this statement: "return;".
  743             return;
  744         }
  745
  746         trace_artist_draw_line(startx, starty, endx, endy);
  747         draw_line(s, startx, starty, endx, endy, false, -1, -1);
  748     }

Fixes: Covertiy CID 1419388 and 1419389 (commit 4765384ce33)
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Acked-by: Sven Schnelle <svens@stackframe.org>
Message-Id: <20200214001303.12873-6-f4bug@amsat.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>