clk: meson-gxbb: Fix HDMI PLL for GXL SoCs

In an attempt to better describe the HDMI PLL, a single DCO clock was
left for GXBB and GXL, but the GXL DCO does not have a pre-multiplier.

This patch adds back a GXL specific HDMI PLL DCO with xtal as parent.

Fixes: 87173557 ("clk: meson: clk-pll: remove od parameters")
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Acked-by: Jerome Brunet <jbrunet@baylibre.com>
Link: http://lkml.kernel.org/r/1541516257-16157-3-git-send-email-narmstrong@baylibre.com