Merge r254306:

 Merge r254306:

 Update PCI drivers to no longer look at the MEMIO-enabled bit in the PCI
 command register.  The lazy BAR allocation code in FreeBSD sometimes
 disables this bit when it detects a range conflict, and will re-enable
 it on demand when a driver allocates the BAR.  Thus, the bit is no longer
 a reliable indication of capability, and should not be checked.  This
 results in the elimination of a lot of code from drivers, and also gives
 the opportunity to simplify a lot of drivers to use a helper API to set
 the busmaster enable bit.

 This changes fixes some recent reports of disk controllers and their
 associated drives/enclosures disappearing during boot.

Submitted by:	jhb
Reviewed by:	jfv, marius, adrian, achim
Approved by:	re

git-svn-id: svn://svn.freebsd.org/base/releng/9.2@254364 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f