staging: lustre: fid: remove seq_fid_alloc_fini() and simplify

seq_fid_alloc_fini() is tiny and only called
from two places in the one function.  We can move
both those calls earlier and merge them so only
one call is needed.  At that point, there is no
value added by having a separate function.

Also instead of using ++ and -- on ->lcs_update to
toggle between 0 and 1, explicitly set to 0 or 1
as appropriate.

Moving the locking earlier means that the code which updates
seq->lcs_fid is now protected, so
ldebugfs_fid_fid_seq_show() now cannot see a torn value.

Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>