arm64: dts: juno: fix OF graph endpoint node names

OF graph endpoint node names should be 'endpoint'. Fix the following
warnings found by dtc:

Warning (graph_endpoint): /hdlcd@7ff50000/port/hdlcd1-endpoint: graph endpont node nameshould be 'endpoint'
Warning (graph_endpoint): /hdlcd@7ff60000/port/hdlcd0-endpoint: graph endpont node nameshould be 'endpoint'
Warning (graph_endpoint): /i2c@7ffa0000/hdmi-transmitter@70/port/tda998x-0-endpoint: graph endpont node name should be 'endpoint'
Warning (graph_endpoint): /i2c@7ffa0000/hdmi-transmitter@71/port/tda998x-1-endpoint: graph endpont node name should be 'endpoint'

Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Acked-by: Liviu Dudau <liviu.dudau@arm.com>
Signed-off-by: Rob Herring <robh@kernel.org>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>