MFC r331797:

Use an accessor function to access ifr_data.

This fixes 32-bit compat (no ioctl command defintions are required
as struct ifreq is the same size).

Reviewed by: kib
Obtained from: CheriBSD
Sponsored by: DARPA, AFRL
Differential Revision: https://reviews.freebsd.org/D14900

Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

The r48589 promised to remove implicit inclusion of if_var.h soon. Prepare
to this event, adding if_var.h to files that do need it. Also, include
all includes that now are included due to implicit pollution via if_var.h

Sponsored by: Netflix
Sponsored by: Nginx, Inc.

Propagate rename of IFF_OACTIVE and IFF_RUNNING to IFF_DRV_OACTIVE and
IFF_DRV_RUNNING, as well as the move from ifnet.if_flags to
ifnet.if_drv_flags. Device drivers are now responsible for
synchronizing access to these flags, as they are in if_drv_flags. This
helps prevent races between the network stack and device driver in
maintaining the interface flags field.

Many __FreeBSD__ and __FreeBSD_version checks maintained and continued;
some less so.

Reviewed by: pjd, bz
MFC after: 7 days

Stop embedding struct ifnet at the top of driver softcs. Instead the
struct ifnet or the layer 2 common structure it was embedded in have
been replaced with a struct ifnet pointer to be filled by a call to the
new function, if_alloc(). The layer 2 common structure is also allocated
via if_alloc() based on the interface type. It is hung off the new
struct ifnet member, if_l2com.

This change removes the size of these structures from the kernel ABI and
will allow us to better manage them as interfaces come and go.

Other changes of note:
- Struct arpcom is no longer referenced in normal interface code.
Instead the Ethernet address is accessed via the IFP2ENADDR() macro.
To enforce this ac_enaddr has been renamed to _ac_enaddr.
- The second argument to ether_ifattach is now always the mac address
from driver private storage rather than sometimes being ac_enaddr.

Reviewed by: sobomax, sam

Start each of the license/copyright comments with /*-, minor shuffle of lines

Eliminate multiple __FBSDID and sys/cdefs.h.

Use __FBSDID().
Also some minor style cleanups.

Make open channels persist across ifconfig down and up. All channels
that are not currently closing when the interface is configured down
will be brough up as soon as the interface is configured up.

Remove the ATMIOCENA and ATMIOCDIS ioctl. Everyting has been converted
to use the new OPENVCC and CLOSEVCC calls that allow the sepcification
of traffic parameters for the connections.

Honor the ATMIO_FLAG_ASYNC for asynchronuous open/close of VCs.

Send events for VCC state changes, ACR rate changes and interface state
changes.

This is a driver for IDT77252 based ATM interfaces. It has been tested
with a ProATM-155 and an IDT evaluation board and should also work
with a ProATM-25 (it seems to work at least, I cannot really measure
what the card emits). The driver has been tested on i386 and sparc64,
but should work an other archs also. It supports UBR, CBR, ABR and VBR;
AAL0, AAL5 and AALraw. As an additional feature VCI/VPI 0/0 can be
opened for receiving in AALraw mode and receives all cells not claimed
by other open VCs (even cells with invalid GFC, VPI and VCI fields and
OAM cells).

Thanks to Christian Bucari from ProSum for lending two cards and answering
my questions.