nshlib/nsh_console.c: Add fflush to nsh_consolewrite().  This resolves this problem:
> cat /dev/ttyCP &
> echo ls >/dev/ttyCP
Can't get the 'ls' result immediately, because 'cat' cmd uses nsh_consolewrite() and that uses fwrite with no fflush. We can get the 'ls' result after type '\n', because nsh will fflush output when get '\n'.
@@ -186,6 +186,11 @@ static ssize_t nsh_consolewrite(FAR struct nsh_vtbl_s *vtbl,
_err("ERROR: [%d] Failed to send buffer: %d\n",
pstate->cn_outfd, errno);
}
+
+ /* Flush the data to the output stream */
+
+ fflush(pstate->cn_outstream);
+
return ret;
#else
/* REVISIT: buffer may not be NUL-terminated */
