ARM: dts: imx6sx: Specify IMX6SX_CLK_IPG as "ipg" clock to SDMA

[ Upstream commit 8979117765c19edc3b01cc0ef853537bf93eea4b ]

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 IMX6SX_CLK_SDMA results in driver incorrectly thinking that
ratio is 1:1 which results in broken SDMA funtionality. Fix the code
to specify IMX6SX_CLK_IPG as "ipg" clock for SDMA, to avoid detecting
incorrect clock ratio.

Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
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
Signed-off-by: Shawn Guo <shawnguo@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>