ARM: omap2: fix missing tick_broadcast() prototype

omap2 contains a hack to define tick_broadcast() on non-SMP
configurations in place of the normal SMP definition. This one
causes a warning because of a missing prototype:

arch/arm/mach-omap2/board-generic.c:44:6: error: no previous prototype for 'tick_broadcast'

Make sure to always include the header with the declaration.

Fixes: d86ad463 ("ARM: OMAP2+: Fix regression for using local timer on non-SMP SoCs")
Acked-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Link: https://lore.kernel.org/r/20230516153109.514251-9-arnd@kernel.org


Signed-off-by: Arnd Bergmann <arnd@arndb.de>