checkpatch: do not complain about positive return values starting with EPOLL

checkpatch complains about positive return values of poll functions.
Example:

WARNING: return of an errno should typically be negative (ie: return -EPOLLIN)
+		return EPOLLIN;

Poll functions return positive values.  The defines for the return values
of poll functions all start with EPOLL, resulting in a number of false
positives.  An often used workaround is to assign poll function return
values to variables and returning that variable, but that is a less than
perfect solution.

There is no error definition which starts with EPOLL, so it is safe to
omit the warning for return values starting with EPOLL.

Link: https://lkml.kernel.org/r/20210622004334.638680-1-linux@roeck-us.net


Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Acked-by: Joe Perches <joe@perches.com>
Cc: Ricardo Ribalda <ribalda@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>