perf/arm_pmu_platform: fix tests for platform_get_irq() failure

The platform_get_irq() returns negative error codes.  It can't actually
return zero.

Signed-off-by: Yu Zhe <yuzhe@nfschina.com>
Link: https://lore.kernel.org/r/20220825011844.8536-1-yuzhe@nfschina.com


Signed-off-by: Will Deacon <will@kernel.org>