Fix docbook regression

Hello, Linus,

Commit 764f80798b95 ("doc: Add RCU files to docbook-generation files"), which is in v4.14-rc1, added :external: options for RCU source files in the file Documentation/core-api/kernel-api.rst. However, this now means nothing, and furthermore breaks builds of the docbook, which has led to popular demand for this to be fixed in v4.14:

	lkml.kernel.org/r/[email protected]

This series therefore contains the following two patches:

1. Remove the erroneous :external: options.

2. Fix the many docbook build complaints that have crept into RCU's
docbook comment headers. These fixes include one non-comment change where the name of rcu_sync_func()'s argument is changed to match RCU convention.

Thanx, Paul

------------------------------------------------------------------------

 Documentation/core-api/kernel-api.rst |   14 --------------
 include/linux/rculist.h               |    2 +-
 include/linux/rcupdate.h              |   22 ++++++++++++++--------
 include/linux/srcu.h                  |    1 +
 kernel/rcu/srcutree.c                 |    2 +-
 kernel/rcu/sync.c                     |    9 ++++++---
 kernel/rcu/tree.c                     |   18 ++++++++++--------
 7 files changed, 33 insertions(+), 35 deletions(-)