FreeBSD_HEAD_i386 - Build #2371 - Fixed

FreeBSD_HEAD_i386 - Build #2371 - Fixed:

Build information: https://jenkins.FreeBSD.org/job/FreeBSD_HEAD_i386/2371/
Full change log: https://jenkins.FreeBSD.org/job/FreeBSD_HEAD_i386/2371/changes
Full build log: https://jenkins.FreeBSD.org/job/FreeBSD_HEAD_i386/2371/console

Change summaries:

295762 by zbb:
Fix build for i386 and arm64 after r295755

- Take bus_space_tag_t type into consideration when returning
  default, zero value.
- Include missing rman.h required by ofw_pci.h

295761 by br:
Increase kernel and user VA space.
This allows us to boot with more than 128MB of physical memory.

Sponsored by:	DARPA, AFRL
Sponsored by:	HEIF5

295760 by se:
Make WARNS=6 safe.

Tested with Clang 3.7.1, GCC 4.2.1 and GCC 4.8.5 on amd64.