bootutil: Remove area ID parameter from fixup_revert

The fixup_revert has been switched to use boot_read_swap_state,
from boot_read_swap_state_by_id, and no longer needs the ID
parameter.  It can now get swap state information by flash_area
object pointer, which is provided as 3rd parameter.

Signed-off-by: Dominik Ermel <dominik.ermel@nordicsemi.no>