ps3: vuart: fix error path locking

This stray down would cause a permanent sleep which doesn't seem correct.
The other uses of this semaphore appear fairly mutex like it's even
initialized with init_MUTEX() ..  So here a patch for removing this one
down().

Signed-off-by: Geoff Levand <geoffrey.levand@am.sony.com>
Signed-off-by: Daniel Walker <dwalker@mvista.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>