Add the firmware blob required to use the sdma hardware in the imx6

Add the firmware blob required to use the sdma hardware in the imx6
processor, and its associated license text (which is similar to a
bsd-3-clause, but with a prohibition against decompiling).  Install a copy
of the license in /usr/share/doc/legal/imx, to comply with the license terms
that requires a copy of the license to be delivered along with the firmware.

Obtained from:	https://git.kernel.org/pub/scm/linux/kernel/git/firmware/linux-firmware.git/tree/imx/sdma/sdma-imx6q.bin https://git.kernel.org/pub/scm/linux/kernel/git/firmware/linux-firmware.git/tree/LICENSE.sdma_firmware