HID: map telephony usage page

Currently HID code maps usages from telephony page into BTN_0, BTN_1, etc
keys which get interpreted by mousedev and userspace as left/right/middle
button clicks, which is not really helpful.

This change adds mappings for usages that have corresponding input event
definitions, and leaves the rest unmapped. This can be changed when
there are userspace consumers for more telephony usages.

Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>