ARM: nomadik: fix clocksource warning

The clocksource API has changed slightly, which causes a harmless
warning:

/git/arm-soc/drivers/clocksource/nomadik-mtu.c:259:28: warning: 'nmdk_timer_match' defined but not used [-Wunused-variable]
 static struct of_device_id nmdk_timer_match[] __initconst = {
                            ^

Fortunately, the same API change also lets us simplify the code
while removing the warning.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Olof Johansson <olof@lixom.net>