hid: egalax: Add support for Wetab (726b)

This patch adds support for another Wetab device (726b), and grabs it
accordingly in hid-core.

[rydberg@euromail.se: rename and log message changes]
Signed-off-by: Andy Ross <andy@plausible.org>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Henrik Rydberg <rydberg@euromail.se>