drivers/clocksource/tcb_clksrc.c: fix init sequence

setup_irq() was called before clockevents_register_device() which is
needed by the irq handler.  Bug was reproducible by restarting the
kernel using kexec (reliable crash).

Signed-off-by: Nikolaus Voss <n.voss@weinmann.de>
Cc: David Brownell <dbrownell@users.sourceforge.net>
Cc: Haavard Skinnemoen <hskinnemoen@atmel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>