xfs: use kvfree() in xlog_cil_free_logvec()

The xfs_log_vec items are allocated by xlog_kvmalloc(), and so need
to be freed with kvfree. This was missed when coverting from the
kmem_free() API.

Fixes: 49292576 ("xfs: convert kmem_free() for kvmalloc users to kvfree()")
Reported-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Tested-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>