quota: Rename quota_update_limits() to quota_read_all_dquots()

quota: Rename quota_update_limits() to quota_read_all_dquots()

quota_update_limits() is a misnomer because what it actually does is
that it updates 'usage' counters and leaves 'limit' counters intact.
Rename quota_update_limits() to quota_read_all_dquots() and while
changing prototype also add a flags argument so that callers can control
which quota information is actually updated from the disk.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>