k210: dts: add missing power bus clocks

Linux drivers for many of the K210 peripherals depend on the power bus
clock to be specified. Add the missing clocks and their names to avoid
problems when booting Linux using u-boot DT.

Signed-off-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Signed-off-by: Niklas Cassel <niklas.cassel@wdc.com>
Reviewed-by: Sean Anderson <seanga2@gmail.com>