drivers/perf: arm_dsu_pmu: Avoid duplicate printouts

platform_get_irq() already screams on failure, so the redundant call to
dev_err() can be removed.

Signed-off-by: Tang Bin <tangbin@cmss.chinamobile.com>
Link: https://lore.kernel.org/r/20200402115940.4928-1-tangbin@cmss.chinamobile.com


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