The text ranging from "subsystem__event_name" to "raw_syscalls__sys_enter()"
is interpreted by asciidoc as a pair of unconstrained text formatting markers.

The result is that the manual page displayed this text as underlined,
and the HTML pages displayed this text as italicized. Escape the first
double-underscore to prevent this.

https://docs.asciidoctor.org/asciidoc/latest/syntax-quick-reference/Signed-off-by: NStephen Brennan <stephen.s.brennan@oracle.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lore.kernel.org/lkml/20210806204502.110305-1-stephen.s.brennan@oracle.comSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>