board: tec-ng: Do not make directories in a board Makefile

Commit e5c5301f refactored the build system not to make
directories in board makefiles.
But commit 8f380381 create directories again in
board/avionic-design/tec-ng/Makefile.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Cc: Alban Bedel <alban.bedel@avionic-design.de>

board/avionic-design/tec-ng/Makefile

@@ -5,8 +5,6 @@
 # SPDX-License-Identifier:	GPL-2.0+
 #
 
-$(shell mkdir -p $(obj)../common $(obj)../../nvidia/common)
-
 obj-y	:= ../common/tamonten-ng.o
 
 include ../../nvidia/common/common.mk