arm64: perf: Fix the pmu node name in warning message

With commit d5efd9cc ("arm64: pmu: add support for interrupt-affinity
property"), we print a warning when we find a PMU SPI with a missing
missing interrupt-affinity property in a pmu node. Unfortunately, we
pass the wrong (NULL) device node to of_node_full_name, resulting in
unhelpful messages such as:

 hw perfevents: Failed to parse <no-node>/interrupt-affinity[0]

This patch fixes the name to that of the pmu node.

Fixes: d5efd9cc (arm64: pmu: add support for interrupt-affinity property)
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Suzuki K. Poulose <suzuki.poulose@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>