TAKE - remove some dead code

[Steve Lord <lord@xxxxxxx>]

Small chunk of pagebuf code which was not used.

Date:  Wed Mar  6 11:44:58 PST 2002
Workarea:  jen.americas.sgi.com:/src/lord/xfs-linux.2.4

The following file(s) were checked into:
  bonnie.engr.sgi.com:/isms/slinx/2.4.x-xfs


Modid:  2.4.x-xfs:slinx:113413a
linux/fs/xfs/xfs_buf.h - 1.83
        - remove xfs_bwait_unpin, no one uses it.

linux/fs/xfs/pagebuf/page_buf.c - 1.13
linux/fs/xfs/pagebuf/page_buf.h - 1.7
        - remove pagebuf_wait_unpin no one uses it