init: clear root_wait on all invalid root= strings

Instead of only clearing root_wait in devt_from_partuuid when the UUID
format was invalid, do that in parse_root_device for all strings that
failed to parse.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20230531125535.676098-15-hch@lst.de


Signed-off-by: Jens Axboe <axboe@kernel.dk>