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