btrfs: Use WARN_ON()'s return value in place of WARN_ON(1)

btrfs: Use WARN_ON()'s return value in place of WARN_ON(1)

Use WARN_ON()'s return value in place of WARN_ON(1) for cleaner source
code that outputs a more descriptive warnings. Also fix the styling
warning of redundant braces that came up as a result of this fix.

Signed-off-by: Dulshani Gunawardhana <[email protected]>
Reviewed-by: Zach Brown <[email protected]>
Signed-off-by: Josef Bacik <[email protected]>
Signed-off-by: Chris Mason <[email protected]>