TARGET_MCUXpresso_MCUS: fix lp ticker init function

In case when lp ticker is already initialized the ticker interrupt should be disabled.

targets/TARGET_Freescale/TARGET_MCUXpresso_MCUS/api/lp_ticker.c

@@ -63,8 +63,7 @@ void lp_ticker_init(void)
 
         lp_ticker_inited = true;
     } else {
-        LPTMR_DisableInterrupts(LPTMR0, kLPTMR_TimerInterruptEnable);
-        NVIC_EnableIRQ(LPTMR0_IRQn);
+        lp_ticker_disable_interrupt();
     }
 }