xfs: split and cleanup xfs_log_reserve

Split the log regrant case out of xfs_log_reserve into a separate function,
and merge xlog_grant_log_space and xlog_regrant_write_log_space into their
respective callers.  Also replace the XFS_LOG_PERM_RESERV flag, which easily
got misused before the previous cleanups with a simple boolean parameter.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Mark Tinguely <tinguely@sgi.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Ben Myers <bpm@sgi.com>

diff --cc fs/xfs/xfs_log.c
Simple merge

diff --cc fs/xfs/xfs_log.h
Simple merge

diff --cc fs/xfs/xfs_log_priv.h
Simple merge

diff --cc fs/xfs/xfs_trace.h
Simple merge

diff --cc fs/xfs/xfs_trans.c
Simple merge