Add a helper function to the swapout daemon's deactivation code.

[markj]

Summary

vm_swapout_object_deactivate_pages() is renamed to
vm_swapout_object_deactivate(), and the loop body is moved into the new
vm_swapout_object_deactivate_page(). This makes the code a bit easier
to follow and is in preparation for some functional changes.

[alc]

sys/vm/vm_swapout.c

238

bool?

[markj]

Rename remove_mode and convert it to a bool.