clk: mediatek: Add hdmi_ref HDMI PHY PLL reference clock output

The configurable hdmi_ref output of the PLL block is derived from
the tvdpll_594m clock signal via a configurable PLL post-divider.
It is used as the PLL reference input to the HDMI PHY module.

Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Acked-by: James Liao <jamesjj.liao@mediatek.com>
Acked-by: Stephen Boyd <sboyd@codeaurora.org>

include/dt-bindings/clock/mt8173-clk.h

@@ -176,7 +176,8 @@
 #define CLK_APMIXED_LVDSPLL		13
 #define CLK_APMIXED_MSDCPLL2		14
 #define CLK_APMIXED_REF2USB_TX		15
-#define CLK_APMIXED_NR_CLK		16
+#define CLK_APMIXED_HDMI_REF		16
+#define CLK_APMIXED_NR_CLK		17
 
 /* INFRA_SYS */