coresight: trbe: Fix return value check in arm_trbe_register_coresight_cpu()

mainline inclusion
from mainline-v5.13-rc1
commit 68d400c0
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I8BC14
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=68d400c079978f649e7f63aba966d219743edd64



--------------------------------

In case of error, the function devm_kasprintf() returns NULL
pointer not ERR_PTR(). The IS_ERR() test in the return value
check should be replaced with NULL test.

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Link: https://lore.kernel.org/r/20210409094901.1903622-1-weiyongjun1@huawei.com


Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Junhao He <hejunhao3@huawei.com>