coresight: etm: perf: Make symbol 'format_attr_contextid' static

coresight: etm: perf: Make symbol 'format_attr_contextid' static

The sparse tool complains as follows:

drivers/hwtracing/coresight/coresight-etm-perf.c:61:25: warning:
 symbol 'format_attr_contextid' was not declared. Should it be static?

This symbol is not used outside of coresight-etm-perf.c, so this
commit marks it static.

Link: https://lore.kernel.org/r/20210308123250.2417947-1-weiyongjun1@huawei.com
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/20210407160007.418053-3-mathieu.poirier@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>