ARM: 7261/1: clocksource/ux500-prcmu: fix sched_clock breakage

commit 2f0778af adding
runtime-selectable sched_clock() forgot to patch this
driver down in drivers/clocksource, this patch fixes
the problem.

Reported-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Linus Walleij <linus.walleij@stericsson.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>