MFamd64: Add a machdep.bootmethod sysctl to inform the installer which
firmware method was used for booting.  This is hardcoded to BIOS on i386.

PR:		192962
Reviewed by:	nwhitehorn
MFC after:	1 week


git-svn-id: svn+ssh://svn.freebsd.org/base/head@270826 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f
Fix a typo.


git-svn-id: svn+ssh://svn.freebsd.org/base/head@270827 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f