HID: fix parsing of local delimiter with size 0

Acording to HID standard 1.11, value 0 allows for size being 0.
Local delimiter tag has has 0 one of the possible values.

Therefore we need to handle this case properly, to be fully compliant
with the specification.

Reported-by: Marcin Tolysz <tolysz@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>