pinctrl: meson-gxbb: add hdmi related pins

The GXBB pinctrl is missing pins related to HDMI, namely hot plug
detection (hpd) and I2C (sda + scl).

This fixes HDMI support for GXBB in u-boot.

Reported-by: Mohammad Rasim <mohammad.rasim96@gmail.com>
Signed-off-by: Maxime Jourdan <mjourdan@baylibre.com>
Acked-by: Neil Armstrong <narmstrong@baylibre.com>
Tested-by: Mohammad Rasim <mohammad.rasim96@gmail.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>