ARM: dts: imx6qdl: Specify IMX6QDL_CLK_IPG as "ipg" clock to SDMA

ARM: dts: imx6qdl: Specify IMX6QDL_CLK_IPG as "ipg" clock to SDMA

Since 25aaa75df1e6 SDMA driver uses clock rates of "ipg" and "ahb"
clock to determine if it needs to configure the IP block as operating
at 1:1 or 1:2 clock ratio (ACR bit in SDMAARM_CONFIG). Specifying both
clocks as IMX6QDL_CLK_SDMA results in driver incorrectly thinking that
ratio is 1:1 which results in broken SDMA funtionality(this at least
breaks RAVE SP serdev driver on RDU2). Fix the code to specify
IMX6QDL_CLK_IPG as "ipg" clock for SDMA, to avoid detecting incorrect
clock ratio.

Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Reviewed-by: Lucas Stach <l.stach@pengutronix.de>
Cc: Angus Ainslie (Purism) <angus@akkea.ca>
Cc: Chris Healy <cphealy@gmail.com>
Cc: Lucas Stach <l.stach@pengutronix.de>
Cc: Fabio Estevam <fabio.estevam@nxp.com>
Cc: Shawn Guo <shawnguo@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Tested-by: Adam Ford <aford173@gmail.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>