arm64: dts: imx8mp: Fix LDB clocks property

The "media_ldb_root_clk" is the gate clock to enable or disable the clock
provided by CCM(Clock Control Module) to LDB instead of the "media_ldb"
clock which is the parent of the "media_ldb_root_clk" clock as a composite
clock.  Fix LDB clocks property by referencing the "media_ldb_root_clk"
clock instead of the "media_ldb" clock.

Fixes: e7567840 ("arm64: dts: imx8mp: Reorder clock and reg properties")
Fixes: 94e6197d ("arm64: dts: imx8mp: Add LCDIF2 & LDB nodes")
Signed-off-by: Liu Ying <victor.liu@nxp.com>
Reviewed-by: Marek Vasut <marex@denx.de>
Reviewed-by: Alexander Stein <alexander.stein@ew.tq-group.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>