arm: set cntfrq_el0 if CONFIG_COUNTER_FREQUENCY is valid

Since COUNTER_FREQUENCY is obselete, so set cntfrq_el0 if
CONFIG_COUNTER_FREQUENCY is valid

Signed-off-by: Peng Fan <peng.fan@nxp.com>
Reviewed-by: Philipp Tomsich <philipp.tomsich@vrull.eu>