ENGR00218013-5 HDMI: Add SDMA to help HDMI audio support multi buffer

ENGR00218013-5 HDMI: Add SDMA to help HDMI audio support multi buffer

For chip version easily than TO1.1, HDMI use internel DMA enginue for
audio tranfer. Due to capability of HDMI module, FIFO underrun is
unavoidable.

For chip TO 1.2, introducing SDMA to help HDMI audio DMA. With the help
of SDMA, HDMI audio can use ping-pong buffer mechanism and FIFO underrun
can be avoid.

In this path: Add SDMA support for i.MX6Q later than TO1.2.

Signed-off-by: Chen Liangjun <b36089@freescale.com>