Fix to return negative error code -ENOMEM from the error handling
case instead of 0, as done elsewhere in this function.

Fixes: 53c218da ("driver/perf: Add PMU driver for the ARM DMC-620 memory controller")
Reported-by: NHulk Robot <hulkci@huawei.com>
Signed-off-by: NWei Yongjun <weiyongjun1@huawei.com>
Link: https://lore.kernel.org/r/20210312080421.277562-1-weiyongjun1@huawei.comSigned-off-by: NWill Deacon <will@kernel.org>