kernel/acpica: Add tunables for editing the _OSI string list.

kernel/acpica: Add tunables for editing the _OSI string list.

ACPICA has a built-in list of supported _OSI strings. A query on any of
those strings returns TRUE. It is meant to help the ASL code determine
which OS it is dealing with. See AcpiDefaultSupportedInterfaces[] in
utosi.c for the full list.

This commit adds two tunables, hw.acpi.{install,remove}_interface,
for adding to and removing from that list. Their contents are comma
separated and leading white space is ignored.

Examples:

# Add "FreeBSD" to the list of supported _OSI strings,
# i.e. _OSI("FreeBSD") from ASL will return TRUE.
#
hw.acpi.install_interface="FreeBSD"

# Remove "Windows 2000" and "Windows 2001" from the list
# of supported _OSI strings, i.e. _OSI("Windows 2000") and
# _OSI("Windows 2001") from ASL will return FALSE.
#
hw.acpi.remove_interface="Windows 2000, Windows 2001"

Taken-from: FreeBSD