UPSTREAM: scripts: kernel-doc: Fix syntax error due to undeclared args variable

The backport of commit 3080ea5553cc ("stddef: Introduce
DECLARE_FLEX_ARRAY() helper") to 5.10.y (as a prerequisite of another
fix) modified scripts/kernel-doc and introduced a syntax error:

Global symbol "$args" requires explicit package name (did you forget to declare "my $args"?) at ./scripts/kernel-doc line 1236.
Global symbol "$args" requires explicit package name (did you forget to declare "my $args"?) at ./scripts/kernel-doc line 1236.
Execution of ./scripts/kernel-doc aborted due to compilation errors.

Note: The issue could be fixed in the 5.10.y series as well by
backporting e86bdb24375a ("scripts: kernel-doc: reduce repeated regex
expressions into variables") but just replacing the undeclared args back
to ([^,)]+) was the most straightforward approach. The issue is specific
to the backport to the 5.10.y series. Thus there is as well no upstream
commit for this change.

Fixes: 443b16ee3d9c ("stddef: Introduce DECLARE_FLEX_ARRAY() helper") # 5.10.y
Reported-by: Ben Hutchings <[email protected]>
Link: https://lore.kernel.org/regressions/[email protected]/T/#u
Link: https://bugs.debian.org/1064035
Signed-off-by: Salvatore Bonaccorso <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

(cherry picked from commit d430e298549b31a8607879fdb061c211fb9bbc4a)
Change-Id: I4391a0851ead8b3e7a11b3a420ba9cd3a3c38d28
Signed-off-by: Michael Bestas <[email protected]>

scripts/kernel-doc

@@ -1233,7 +1233,7 @@ sub dump_struct($$) {
 	# replace DECLARE_KFIFO_PTR
 	$members =~ s/DECLARE_KFIFO_PTR\s*\(([^,)]+),\s*([^,)]+)\)/$2 \*$1/gos;
 	# replace DECLARE_FLEX_ARRAY
-	$members =~ s/(?:__)?DECLARE_FLEX_ARRAY\s*\($args,\s*$args\)/$1 $2\[\]/gos;
+	$members =~ s/(?:__)?DECLARE_FLEX_ARRAY\s*\(([^,)]+),\s*([^,)]+)\)/$1 $2\[\]/gos;
 	my $declaration = $members;
 
 	# Split nested struct/union elements as newer ones