arm64: dts: imx8mm: Add opp-suspend property to OPP table

Add opp-suspend property to each OPP, the of opp core will
select the OPP HW supported and with highest rate to be
suspend opp, it will speed up the suspend/resume process.

Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>