dts: common: nordic: nrf54h20: add CANPLL

Define CANPLL, an AUXPLL IP instance used by the CAN IP. PLL settings
are hardcoded in SoC files, as this PLL should not be configured by the
application. It is meant to always run at 80 MHz.

Signed-off-by: Gerard Marull-Paretas <gerard@teslabs.com>