arm64: dts: imx8mp: Fix pgc_mlmix location

[ Upstream commit 106f68fc ]

The pgc_mlmix shows a power-domain@24, but the reg value is
IMX8MP_POWER_DOMAIN_MLMIX which is set to 4.

The stuff after the @ symbol should match the stuff referenced
by 'reg' so reorder the pgc_mlmix so it to appear as power-domain@4.

Fixes: 834464c8 ("arm64: dts: imx8mp: add mlmix power domain")
Fixes: 4bedc468 ("arm64: dts: imx8mp: Add NPU Node")
Signed-off-by: Adam Ford <aford173@gmail.com>
Reviewed-by: Peng Fan <peng.fan@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>
Signed-off-by: Sasha Levin <sashal@kernel.org>