MFC r309491: Build smbios.ko as a module for amd64 and i386

MFC r309491: Build smbios.ko as a module for amd64 and i386

For whatever reason, smapi, smbios, vpd are all under the "bios" directory.
smapi is only for i386, so the entire "bios" directory is only built for
i386. Break smapi out, and make only it i386-specific. Then, build the
"bios" directory for both amd64 and i386.

Because 'sys/modules/Makefile' was refactored after stable/10 was branched,
the diff for that file is different from that of the original commit. They
are functionally equivalent.

git-svn-id: svn://svn.freebsd.org/base/stable/10@309842 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f