Fix a few nits in vm_pqbatch_process_page().
- Don't bother masking off non-queue state flags when loading the page's atomic state, since it is only required for one of the function's assertions. Update the assertion instead.
- Remove an incorrect comment regarding synchronization with the page daemon. The page daemon only ever checks for PGA_ENQUEUED with the page queue lock held.
- When clearing requeue flags, only clear the flags that have been acted upon.
Reviewed by: kib (previous version)
Discussed with: alc
Tested by: pho (part of a larger patch)
MFC after: 1 week
Sponsored by: Netflix
Differential Revision: https://reviews.freebsd.org/D21368