Insta-MFC of r199084,199108:

Insta-MFC of r199084,199108:
   Increase the size of the OFW translations buffer to handle G5 systems
   that use many translation regions in firmware, and add bounds checking
   to prevent buffer overflows in case even the new value is exceeded.

Short MFC requested by re since the problem this fixes breaks CD boot on
most G5 systems, making them uninstallable.

Reported by:	Jacob Lambert
Approved by:	re (kensmith,kib)
Requested by:	re

git-svn-id: svn://svn.freebsd.org/base/stable/8@199110 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f