ARM: 8357/1: perf: fix memory leak when probing PMU PPIs

Commit 338d9dd3 ("ARM: 8351/1: perf: don't warn about missing
interrupt-affinity property for PPIs") added a check for PPIs so that
we avoid parsing the interrupt-affinity property for these naturally
affine interrupts.

Unfortunately, this check can trigger an early (successful) return and
we will leak the irqs array. This patch fixes the issue by reordering
the code so that the check is performed before any independent
allocation.

Reported-by: David Binderman <dcb314@hotmail.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>