Enable HW media decoder in NanoPC T6

Enable HW media decoder in NanoPC T6

The meta-rockchip has gstreamer-rockchip recipe.  It enables HW
media decoder in rockchip boards.
Current integration did not enable gstreamer-rockchip.
This patch enable gstreamer-rockchip.

Bug-AGL: SPEC-5319

Change-Id: I2cfa34b4d8daf0f0830de288b07f0ceddb99e210
Signed-off-by: Naoto Yamaguchi <naoto.yamaguchi@aisin.co.jp>
Reviewed-on: https://gerrit.automotivelinux.org/gerrit/c/AGL/meta-agl/+/30642
Tested-by: Jenkins Job builder account
ci-image-boot-test: Jenkins Job builder account
Reviewed-by: Jan-Simon Moeller <jsmoeller@linuxfoundation.org>
ci-image-build: Jenkins Job builder account