exceptions: fork exception table content from module.h into extable.h

exceptions: fork exception table content from module.h into extable.h

For historical reasons (i.e. pre-git) the exception table stuff was
buried in the middle of the module.h file.  I noticed this while
doing an audit for needless includes of module.h and found core
kernel files (both arch specific and arch independent) were just
including module.h for this.

The converse is also true, in that conventional drivers, be they
for filesystems or actual hardware peripherals or similar, do not
normally care about the exception tables.

Here we fork the exception table content out of module.h into a
new file called extable.h -- and temporarily include it into the
module.h itself.

Then we will work our way across the arch independent and arch
specific files needing just exception table content, and move
them off module.h and onto extable.h

Once that is done, we can remove the extable.h from module.h
and in doing it like this, we avoid introducing build failures
into the git history.

The gain here is that module.h gets a bit smaller, across all
modular drivers that we build for allmodconfig.  Also the core
files that only need exception table stuff don't have an include
of module.h that brings in lots of extra stuff and just looks
generally out of place.

Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>