HID: Fix hid_report_len usage

Follow the change of return type u32 of hid_report_len,
fix all the types of variables those get the return value of
hid_report_len to u32, and all other code already uses u32.

Cc: stable@vger.kernel.org
Signed-off-by: Aaron Ma <aaron.ma@canonical.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>