xfsprogs: fix up the noreturn annotations

xfsprogs: fix up the noreturn annotations

The usage function in mkfs needs a noreturn annotation too, otherwise
gcc will complain, similarly the do_msg function in repair would need
it if do_abort is set, but because conditional annotations aren't
possible just clean this area up and inline the do_msg function into
it's callers.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Eric Sandeen <sandeen@sandeen.net>
Signed-off-by: Alex Elder <aelder@sgi.com>