Move the calculations of supported and controlled _OSC features out of
negotiate_os_control() into separate functions.

Link: https://lore.kernel.org/r/20210824122054.29481-3-joro@8bytes.orgSigned-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Rafael J. Wysocki <rafael@kernel.org>