ARM: 7651/1: remove unused smp_timer_broadcast #define

The assignment of clock_event_device::broadcast can be done by timer
core as of 12ad100046: "clockevents: Add generic timer broadcast
function", and the arm code moved over to this as of 3d06770eef: "arm:
Add generic timer broadcast support", but left a dangling #define when
!CONFIG_GENERIC_TIMER_BROADCAST.

This patch removes the now unused #define.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>