clk: imx8mq: add 27m phy pll ref clock

According to pll documentation, the 3rd pll ref clock should be
hdmi phy 27m clock, not dummy clock.

Signed-off-by: Peng Fan <peng.fan@nxp.com>
Reviewed-by: Abel Vesa <abel.vesa@nxp.com>
Link: https://lore.kernel.org/r/20220225090002.2497057-3-peng.fan@oss.nxp.com
Signed-off-by: Abel Vesa <abel.vesa@nxp.com>