counter: ti-ecap-capture: Utilize COUNTER_COMP_FREQUENCY macro

Reduce boilerplate by leveraging the COUNTER_COMP_FREQUENCY() macro to
define the "frequency" extension.

Link: https://lore.kernel.org/r/ZfxhEKdSi1amfcJC@ishi
Signed-off-by: William Breathitt Gray <[e-mail]>

drivers/counter/ti-ecap-capture.c

···
 };
 
 static struct counter_comp ecap_cnt_clock_ext[] = {
-	COUNTER_COMP_SIGNAL_U64("frequency", ecap_cnt_clk_get_freq, NULL),
+	COUNTER_COMP_FREQUENCY(ecap_cnt_clk_get_freq),
 };
 
 static const enum counter_signal_polarity ecap_cnt_pol_avail[] = {