bhyve: maintain RSDT and XSDT by basl

[corvink]

Summary

In a subsquent commit the TPM emulation will build it's own TPM2 table.
This needs to be registered to the RSDT and XSDT. Instead of making the
rsdt and xsdt variables global, we can simply add a helper to basl.

[markj]

usr.sbin/bhyve/basl.c

674

I think these lines are too long.

usr.sbin/bhyve/basl.h

71

These getters do not appear to be defined/used anywhere.

[corvink]

• remove unused getter
• fix style

[markj]

Thanks.