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>

scripts/checkpatch.pl

@@ -5462,7 +5462,7 @@ sub process {
 # Return of what appears to be an errno should normally be negative
 		if ($sline =~ /\breturn(?:\s*\(+\s*|\s+)(E[A-Z]+)(?:\s*\)+\s*|\s*)[;:,]/) {
 			my $name = $1;
-			if ($name ne 'EOF' && $name ne 'ERROR') {
+			if ($name ne 'EOF' && $name ne 'ERROR' && $name !~ /^EPOLL/) {
 				WARN("USE_NEGATIVE_ERRNO",
 				     "return of an errno should typically be negative (ie: return -$1)\n" . $herecurr);
 			}