ext3/balloc.c: local functions should be static

This quites the sparse noise:

warning: symbol 'ext3_trim_all_free' was not declared. Should it be static?

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andreas Dilger <adilger.kernel@dilger.ca>
Signed-off-by: Jan Kara <jack@suse.cz>