uboot-imx

dm: timer: refuse timers with zero clock_rate

If a timer has a zero clock_rate, get_tbclk() will return zero for it,
which will cause tick_to_time() to perform a division-by-zero, which will
crash U-Boot.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Acked-by: Simon Glass <sjg@chromium.org>