Remove the buffer cache's B_PHYS flag. This flag was originally used as

Remove the buffer cache's B_PHYS flag.  This flag was originally used as
part of a severe hack to treat buffers containing 'user' addresses
differently, in particular by using b_offset instead of b_blkno.  Now that
buffer cache buffers only HAVE b_offset (b_*blkno is gone for good), there
is literally no difference between B_PHYS I/O and non-B_PHYS I/O once
the buffer has been handed off to the device.