samples: peripheral: 802154_phy_test: fix nrfx_timer assert

Now this assertion must explicitly check for `0` value
as nrfx 4.0 functions returns errno codes.

Signed-off-by: Nikodem Kastelik <[email protected]>

Author: nika-nordic

samples/peripheral/802154_phy_test/src/periph_proc.c

@@ -99,7 +99,7 @@ void periph_init(void)
 	nrfx_timer_config_t clk_timer_cfg = NRFX_TIMER_DEFAULT_CONFIG(base_frequency);
 
 	err_code = nrfx_timer_init(&clk_timer, &clk_timer_cfg, clk_timer_handler);
-	NRFX_ASSERT(err_code);
+	__ASSERT_NO_MSG(err_code == 0);
 
 	for (int i = 0; i < GPIO_COUNT; ++i) {
 		nrfx_gpiote_t *gpiote = NRF_GPIOTE_FOR_GPIO(i);