arm920t line length cleanup

The recent patch to fixbreakpoints and dcache handling added
a bunch of overlong lines (80+ chars) ... shrink them, and do
the same to a few lines which were already overlong.

Also add a few FIXME comments to nudge (a) replacement of some
magic numbers with opcode macros, which will be much better at
showing what's actually going on, and (b) correct return codes.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>