clocksource: mxs_timer: Add semicolon at end of line

Fix the following build error:

drivers/clocksource/mxs_timer.c:304:1: error: expected ',' or ';' at end of input

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>