• Collapse vfs_vmio_truncate & vfs_vmio_release into a single function.
• Allow vfs_vmio_invalidate() to free the pages, leaving us with a single loop and bufobj lock when B_NOCACHE/B_INVAL is used.
• Eliminate the special B_ASYNC handling on free that has not been relevant for some time.
• Remove the extraneous page busy from vfs_vmio_truncate().

Reviewed by: kib
Tested by: pho
Sponsored by: EMC / Isilon storage division