HID: Move hiddev.txt to the new Documentation/hid directory

With the new Documentation/hid directory, it makes sense to have
hiddev.txt here as well.

Signed-off-by: Alan Ott <alan@signal11.us>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

diff --git a/Documentation/usb/hiddev.txt b/Documentation/hid/hiddev.txt
similarity index 100%
rename from Documentation/usb/hiddev.txt
rename to Documentation/hid/hiddev.txt