Fix for r271182.

Submitted by:	mjg
Pointy hat to:	me, submitter and everyone who urged me to commit
style(9)
Update mixer description for FastTrackPro.

MFC after:	3 days
Use SYSCTL_PROC instead of SYSCTL_VNET_PROC.
Suggested by: glebius@
MFC after: 1 week
Create a common i.MX53 config and use it with the two existing i.MX53
boards.

This is just intended to split the common config entries out, further
cleanup is expected.

Reviewed by:	ian@, rpaulo@ (earlier version)
Differential Revision: https://reviews.freebsd.org/D731
Use union sctp_sockstore instead of struct sockaddr_storage. This
eliminiates some warnings when building in userland.
Thanks to Patrick Laimbock for reporting this issue.
Remove also some unnecessary casts.
There should be no functional change.

MFC after: 1 week