HID: uhid: report to user-space whether reports are numbered

This makes UHID_START include a "dev_flags" field that describes details
of the hid-device in the kernel. The first flags we introduce describe
whether a given report-type uses numbered reports. This is useful for
transport layers that force report-numbers and therefore might have to
prefix kernel-provided HID-messages with the report-number.

Currently, only HoG needs this and the spec only talks about "global
report numbers". That is, it's a global boolean not a per-type boolean.
However, given the quirks we already have in kernel-space, a per-type
value seems much more appropriate.

Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>