clk: sunxi-ng: a64: Add max. rate constraint to video PLLs

Video PLLs on A64 can be set to higher rate that it is actually
supported by HW.

Limit maximum rate to 1008 MHz. This is the maximum allowed rate by BSP
clock driver. Interestengly, user manual specifies maximum frequency to
be 600 MHz. Historically, this data was wrong in some user manuals for
other SoCs, so more faith is put in BSP clock driver.

Signed-off-by: Icenowy Zheng <icenowy@aosc.io>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>