Add the new shm_ino field to struct shmfd.  Missed in 270823.

Reported by:	peter
Pointy hat to:	jhb
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
Fix a typo.