block: remove unnecessary goto labels in debugfs attribute read methods

In some debugfs attribute read methods, failure to acquire the mutex
lock results in jumping to a label before returning an error code.
However this is unnecessary, as we can return the failure code directly,
improving code readability and reducing complexity.

This commit removes the goto labels and ensures that the method returns
immediately upon failing to acquire the mutex lock.

Signed-off-by: Nilay Shroff <nilay@linux.ibm.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20250313115235.3707600-3-nilay@linux.ibm.com


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