smbios: Move smbios driver out from x86 machdep code

Add it to the x86 GENERIC and MINIMAL kernels

Sponsored by: Ampere Computing LLC
Submitted by: Klara Inc.
Reviewed by: rpokala
Differential Revision: https://reviews.freebsd.org/D28738

(cherry picked from commit d0673fe160b04f8162f380926d455dfb966f08fb)