linux-imx

arm64: dts: imx8mm: Add 'dispmix-reset' device

Create a new device node 'dispmix-reset' to describe the
reset controller in DISPMIX to control several submodules
bus and clock reset and enable. All the reset lines can be
divided into three groups: sft_rstn, clk_en and mipi_rst.

Signed-off-by: Fancy Fang <chen.fang@nxp.com>