The bcdDevice field is defined as
|Device release number in binary-coded decimal
in the USB 2.0 specification. We use this field to distinguish the UDCs
from each other. In theory this could be used on the host side to apply
certain quirks if the "special" UDC in combination with this gadget is
used. This hasn't been done as far as I am aware. In practice it would
be better to fix the UDC driver before shipping since a later release
might not need this quirk anymore.

There are some driver in tree (on the host side) which use the bcdDevice
field to figure out special workarounds for a given firmware revision.
This seems to make sense. Therefore this patch converts all gadgets
(except a few) to use the kernel version instead a random 2 or 3 plus
the UDC number. The few that don't report kernel's version are:
- webcam
  This one reports always a version 0x10 so allow it to do so in future.
- nokia
  This one reports always 0x211. The comment says that this gadget works
  only if the UDC supports altsettings so I added a check for this.
- serial
  This one reports 0x2400 + UDC number. Since the gadget version is 2.4
  this could make sense. Therefore bcdDevice is 0x2400 here.

I also remove various gadget_is_<name> macros which are unused. The
remaining few macros should be moved to feature / bug bitfield.
Acked-by: Michal Nazarewicz <mina86@mina86.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Felipe Balbi <balbi@ti.com>