clocksource: Add Freescale Vybrid pit timer support

Add Freescale Vybrid Family period interrupt timer support.

Signed-off-by: Jingchang Lu <b35083@freescale.com>
Reviewed-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Acked-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>

diff --cc drivers/clocksource/Kconfig
Simple merge

diff --cc drivers/clocksource/Makefile
Simple merge

diff --cc drivers/clocksource/vf_pit_timer.c
Simple merge