HACK: arm64: dts: ti: k3-j721e-common-proc-board: Drop dp_link max phy rate

commit 347bc65a87b32154eba5a4fa347a1aaa86f1799b from
git://git.ti.com/ti-linux-kernel/ti-linux-kernel.git

Drop the max phy rate from 5.4Gbps to 2.7Gbps to drop 3840x2160@60fps
resolution causing 'CRTC SYNC LOST' issue.
This limits the max resolution to 3840x2160@30fps and equivalent
resolution.

Signed-off-by: Jayesh Choudhary <j-choudhary@ti.com>
Signed-off-by: Xulin Sun <xulin.sun@windriver.com>