bhyve: add helper to append a basl table without a header
The common style for build an ACPI table will be:
- basl_table_create
- basl_table_append_header
- setup an ACPI_TABLE_* struct
- basl_table_append_bytes (without header)
Add a helper for the last step.
Reviewed by: jhb, markj
Approved by: manu (mentor)
MFC after: 2 weeks
Sponsored by: Beckhoff Automation GmbH & Co. KG
Differential Revision: https://reviews.freebsd.org/D37406
(cherry picked from commit 8897b562abbf1dbc2d6c83d31ed673d5220c3da3)