powerpc: Use of_property_present()

Use of_property_present() to test for property presence rather than
of_get_property(). This is part of a larger effort to remove callers
of of_get_property() and similar functions. of_get_property() leaks
the DT property data pointer which is a problem for dynamically
allocated nodes which may be freed.

Signed-off-by: Rob Herring (Arm) <robh@kernel.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20240731191312.1710417-9-robh@kernel.org