[POWERPC] Fix off-by-one error in setting decrementer on Book E

[Paul Mackerras]

I wrote:

> @@ -601,10 +601,8 @@ void timer_interrupt(struct pt_regs * regs)

That should be

@@ -601,8 +601,6 @@ void timer_interrupt(struct pt_regs * regs)

of course.

Paul.