btrfs: declare free_ipath() via DEFINE_FREE()

btrfs: declare free_ipath() via DEFINE_FREE()

The free_ipath() function was being used as a cleanup function
everywhere. Declare it via DEFINE_FREE() so we can use this function
with the __free() helper.

The name has also been adjusted so it's closer to the type's name.

Signed-off-by: Miquel Sabaté Solà <mssola@mssola.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>