[nrf fromlist] boards: native: nrf_bsim: nrf54l15: Bring back clocks

Do not delete clocks for the bsim target. Clocks are referenced
by peripherals and it can be used to get frequency that clocks
the peripheral.

Upstream PR #: 82901

Signed-off-by: Krzysztof Chruściński <[email protected]>

Author: nordic-krch

boards/native/nrf_bsim/nrf54l15bsim_nrf54l15_cpuapp.dts

@@ -22,7 +22,6 @@
 	};
 
 	/delete-node/ cpus;
-	/delete-node/ clocks;
 	/delete-node/ sw-pwm;
 
 	soc {