HACK: arm64: dts: ti: k3-j784s4-evm: Add serdes_dp_link max-bit-rate

commit c8027d96b2935c97be0b8f04d9d812d97002fd0c from
git://git.ti.com/ti-linux-kernel/ti-linux-kernel.git

Add missing 'cdns,max-bit-rate' property for mhdp phy. If not
specified, the default value takenis 8100 Mbps which often leads to
phy link training errors like:
"CR: max swing reached" and eventually falls back to 1620 Mbps.
Adding 2700 instead of 5400 like other platforms as the latter causes
CRTC SYNC LOST issue for 3840x2160@60fps resolution. So limiting the
phy-rate for max resolution of 3840x2160@30fps.

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