[PATCH] convert ext3's truncate_sem to a mutex

ext3's truncate_sem is always released in the same function it's taken
and it otherwise is a mutex as well..

Signed-off-by: Arjan van de Ven <arjan@infradead.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>