scripts/kernel-doc: Get -export option working again

scripts/kernel-doc: Get -export option working again

Since commit cdd30ebb1b9f ("module: Convert symbol namespace to string
literal"), exported symbols marked by EXPORT_SYMBOL_NS(_GPL) are
ignored by "kernel-doc -export" in fresh build of "make htmldocs".

This is because regex in the perl script for those markers fails to
match the new signatures:

  - EXPORT_SYMBOL_NS(symbol, "ns");
  - EXPORT_SYMBOL_NS_GPL(symbol, "ns");

Update the regex so that it matches quoted string.

Note: Escape sequence of \w is good for C identifiers, but can be
too strict for quoted strings.  Instead, use \S, which matches any
non-whitespace character, for compatibility with possible extension
of namespace convention in the future [1].

Fixes: cdd30ebb1b9f ("module: Convert symbol namespace to string literal")
Link: https://lore.kernel.org/CAK7LNATMufXP0EA6QUE9hBkZMa6vJO6ZiaYuak2AhOrd2nSVKQ@mail.gmail.com/
Signed-off-by: Akira Yokosawa <akiyks@gmail.com>
Cc: Masahiro Yamada <masahiroy@kernel.org>
Tested-by: Randy Dunlap <rdunlap@infradead.org>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/e5c43f36-45cd-49f4-b7b8-ff342df3c7a4@gmail.com