of: make PowerMac cache node search conditional on CONFIG_PPC_PMAC

[ Upstream commit f6707fd6241e483f6fea2caae82d876e422bb11a ]

Cache nodes under the cpu node(s) is PowerMac specific according to the
comment above, so make the code enforce that.

Signed-off-by: Rob Herring <robh@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
1 file changed