firmware: move fw_state_is_done() into UHM section

fw_state_is_done() is only used for UHM so moved into that section.

Cc: Ming Lei <ming.lei@canonical.com>
Cc: Luis R. Rodriguez <mcgrof@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Daniel Wagner <daniel.wagner@bmw-carit.de>