arm64: dts: imx8mp-hummingboard-pulse: fix mini-hdmi dsi port reference

arm64: dts: imx8mp-hummingboard-pulse: fix mini-hdmi dsi port reference

imx8mp.dtsi includes a default port@1 node with an empty placeholder
endpoint intended for linking to a dsi bridge or panel.

HummingBoard Pulse mini-hdmi dtsi described a new endpoint node with a
different label attached.

This duplicate label causes confusion and is suspected to also cause
errors during dsi_attach.

Remove the duplicate node and link to the one defined in soc dtsi.
Further remove the unnecessary attach-bridge property.

Fixes: 2a222aa2bee9 ("arm64: dts: add description for solidrun imx8mp hummingboard variants")
Signed-off-by: Josua Mayer <josua@solid-run.com>
Signed-off-by: Frank Li <Frank.Li@nxp.com>