imx6: fix sdma

Signed-off-by: Luka Perkov <luka@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@37752 3c298f89-4303-0410-b956-a3cf2f4a3e73
kernel: add imx-sdma-fw package

Signed-off-by: Luka Perkov <luka@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@37753 3c298f89-4303-0410-b956-a3cf2f4a3e73
imx6: use kmod-imx-sdma-fw-imx6 by default

Signed-off-by: Luka Perkov <luka@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@37754 3c298f89-4303-0410-b956-a3cf2f4a3e73