HID: thingm: simplify debug output code

Kernel printf format %*ph allows to print small buffers up to 64 bytes.
Make use of it to simplify the debug output code.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>