sysfs: convert BUG_ON to WARN_ON

It's rude to crash the system just because the developer did something
wrong, as it prevents them from usually even seeing what went wrong.

So convert the few BUG_ON() calls that have snuck into the sysfs code
over the years to WARN_ON() to make it more "friendly".  All of these
are able to be recovered from, so it makes no sense to crash.

Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Git-Repo: https://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux-block.git


Git-Commit: de96e9fea7ba56042f105b6fe163447b280eb800
Change-Id: I0008965755b1c83edc097e0f4a1a86e534569bb2
Signed-off-by: Ritesh Harjani <riteshh@codeaurora.org>