arm64: dts: apm: Update Merlin DT PCP PLL clock node for v2 hardware

Update Merlin DT PCP PLL clock node to reflect compatible
string change to reflect v2 hardware.

[dhdang: change patch subject]
Signed-off-by: Loc Ho <lho@apm.com>
Signed-off-by: Duc Dang <dhdang@apm.com>