[PATCH] quota: reiserfs: improve quota credit estimates

Use improved credits estimates for quota operations.  Also reserve space
for a quota operation in a transaction only if filesystem was mounted with
some quota option.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>