[PATCH] ppc64: remove decr_overclock

Now that we have HZ=1000 there is much less of a need for decr_overclock.
Remove it.

Leave spread_lpevents but move it into iSeries_setup.c.  We should look at
making event spreading the default some day.

Signed-off-by: Anton Blanchard <anton@samba.org>
Acked-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>