TAKE - should fix ppc module build

[Steve Lord <lord@xxxxxxx>]

This changes pagebuf to use the __exit directive everywhere rather
than using #if MODULE in some places and __exit in others. This was
a problem on the ppc where I suspect __exit has no effect.

Date:  Fri May 25 15:32:42 PDT 2001
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:95993a
linux/fs/pagebuf/page_buf.c - 1.83
linux/fs/pagebuf/page_buf_locking.c - 1.12
linux/fs/pagebuf/avl.c - 1.4
        - Use __exit consistently in pagebuf code rather than #if MODULE