block: fix rootwait= again

The previous rootwait fix added an -EINVAL return to a completely
bogus superflous branch, fix this.

Fixes: 1341c7d2 ("block: fix rootwait=")
Reported-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Tested-by: Fabio Estevam <festevam@gmail.com>
Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Tested-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20230609051737.328930-1-hch@lst.de


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