clk: rockchip: rk3568: Add PLL rate for 724 MHz

This rate allows to provide a low-jitter 72,4 MHz pixelclock
for a custom eDP panel from the VPLL.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Link: https://lore.kernel.org/r/20240503153329.3906030-1-l.stach@pengutronix.de
Signed-off-by: Heiko Stuebner <heiko@sntech.de>