libpayload/.../PDCurses: Improve compatibility with ncurses

Coverity erroneously complains that we call wmove with x or y == -1,
even though our copy of that function properly checks for that.

But: setsyx is documented to always return OK (even on errors), so let
it do that. (and make coverity happy in the process)

Change-Id: I1bc9ba2a075037f0e1a855b67a93883978564887
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Found-by: Coverity Scan #1260797
Reviewed-on: https://review.coreboot.org/17836
Tested-by: build bot (Jenkins)
Reviewed-by: Martin Roth <martinroth@google.com>

payloads/libpayload/curses/PDCurses/pdcurses/getyx.c

@@ -135,9 +135,14 @@ int setsyx(int y, int x)
         curscr->_leaveit = TRUE;
         return OK;
     }
+    else if (y == -1 || x == -1)
+    {
+        return OK;
+    }
     else
     {
         curscr->_leaveit = FALSE;
-        return wmove(curscr, y, x);
+        wmove(curscr, y, x);
+	return OK;
     }
 }