Synchronize us_ticker to lp_ticker

This is to make implementations of us_ticker/lp_ticker consistent.

Author: ccli8

targets/TARGET_NUVOTON/TARGET_M2351/us_ticker.c

@@ -123,16 +123,7 @@ void us_ticker_init(void)
 
 void us_ticker_free(void)
 {
-    TIMER_T *timer_base = (TIMER_T *) NU_MODBASE(TIMER_MODINIT.modname);
-
-    /* Stop counting */
-    TIMER_Stop(timer_base);
-
-    /* Wait for timer to stop counting and unset active flag */
-    while((timer_base->CTL & TIMER_CTL_ACTSTS_Msk));
-
     /* Disable interrupt */
-    TIMER_DisableInt(timer_base);
     NVIC_DisableIRQ(TIMER_MODINIT.irq_n);
 
     /* Disable IP clock

targets/TARGET_NUVOTON/TARGET_M451/us_ticker.c

@@ -91,16 +91,7 @@ void us_ticker_init(void)
 
 void us_ticker_free(void)
 {
-    TIMER_T *timer_base = (TIMER_T *) NU_MODBASE(TIMER_MODINIT.modname);
-
-    /* Stop counting */
-    TIMER_Stop(timer_base);
-
-    /* Wait for timer to stop counting and unset active flag */
-    while((timer_base->CTL & TIMER_CTL_ACTSTS_Msk));
-
     /* Disable interrupt */
-    TIMER_DisableInt(timer_base);
     NVIC_DisableIRQ(TIMER_MODINIT.irq_n);
 
     /* Disable IP clock */

targets/TARGET_NUVOTON/TARGET_M480/us_ticker.c

@@ -91,16 +91,7 @@ void us_ticker_init(void)
 
 void us_ticker_free(void)
 {
-    TIMER_T *timer_base = (TIMER_T *) NU_MODBASE(TIMER_MODINIT.modname);
-
-    /* Stop counting */
-    TIMER_Stop(timer_base);
-
-    /* Wait for timer to stop counting and unset active flag */
-    while((timer_base->CTL & TIMER_CTL_ACTSTS_Msk));
-
     /* Disable interrupt */
-    TIMER_DisableInt(timer_base);
     NVIC_DisableIRQ(TIMER_MODINIT.irq_n);
 
     /* Disable IP clock */

targets/TARGET_NUVOTON/TARGET_NANO100/us_ticker.c

@@ -93,16 +93,7 @@ void us_ticker_init(void)
 
 void us_ticker_free(void)
 {
-    TIMER_T *timer_base = (TIMER_T *) NU_MODBASE(TIMER_MODINIT.modname);
-
-    /* Stop counting */
-    TIMER_Stop(timer_base);
-
-    /* Wait for timer to stop counting and unset active flag */
-    while((timer_base->CTL & TIMER_CTL_TMR_ACT_Msk));
-
     /* Disable interrupt */
-    TIMER_DisableInt(timer_base);
     NVIC_DisableIRQ(TIMER_MODINIT.irq_n);
 
     /* Disable IP clock */

targets/TARGET_NUVOTON/TARGET_NUC472/us_ticker.c

@@ -90,16 +90,7 @@ void us_ticker_init(void)
 
 void us_ticker_free(void)
 {
-    TIMER_T *timer_base = (TIMER_T *) NU_MODBASE(TIMER_MODINIT.modname);
-
-    /* Stop counting */
-    TIMER_Stop(timer_base);
-
-    /* Wait for timer to stop counting and unset active flag */
-    while((timer_base->CTL & TIMER_CTL_ACTSTS_Msk));
-
     /* Disable interrupt */
-    TIMER_DisableInt(timer_base);
     NVIC_DisableIRQ(TIMER_MODINIT.irq_n);
 
     /* Disable IP clock */