dts: adsp: ace15: replace hp with ipll clock

The ACE family platforms do not have LP/HP RING OSC clocks. They were
replaced by the ACE IP integrated PLL clock. Selecting LP or HP in
CLKCTL will result in enabling IPLL.

Clock can supply frequencies for both replaced clocks, default frequency
equals to 393.2 MHz.

Signed-off-by: Tomasz Leman <tomasz.m.leman@intel.com>