Removed some of experimental code.

Style fix.

Pick up https://svnweb.freebsd.org/base/head/sys/amd64/amd64/pmap.c?r1=329171&r2=329187

Intention of these changes were to improve reuse of code and also reduce number of locks.

vm_page_free_phys_pglist(&pgl) was removed once by a mistake.

Renamed the function and updated styles based on comments.

Removed #if 0 and added a blank line in swp_pager_launder_vmpage().

Simplify "offset" adjustments.

Adjusted styles.
Removed object argument from 2 swp_pager_*_vmpage functions

Renamed to vm_page_free_zero_pages() and it takes boolean_t to update wire count.

Call atomic_subtract_int(&vm_cnt.v_wire_count, count), too if a caller instructs so.

Replaced pmap_free_zero_pages with vm_page_free_spglist().
Fixed styles.
I will handle wire_count upon next changeset.

It started with confusing blist_free() function comment.
I had thought the comment was wrong and asked to remove it and created https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=223392