EFM32: Fixed pwmout_all_inactive being inversed

If one of the CC channel pins is enabled, `pwmout_all_inactive` it
means a channel is active so it should return `true`.

This commit also contains some cleanup in `pwm_init`.

Author: Seppe Stas

targets/TARGET_Silicon_Labs/TARGET_EFM32/pwmout_api.c

@@ -131,7 +131,7 @@ bool pwmout_all_inactive(void) {
         return true;
     }
 #else
-    if(PWM_TIMER->ROUTE & (TIMER_ROUTE_CC0PEN | TIMER_ROUTE_CC1PEN | TIMER_ROUTE_CC2PEN)) {
+    if (!(PWM_TIMER->ROUTE & (TIMER_ROUTE_CC0PEN | TIMER_ROUTE_CC1PEN | TIMER_ROUTE_CC2PEN))) {
         return true;
     }
 #endif
@@ -210,10 +210,11 @@ void pwmout_init(pwmout_t *obj, PinName pin)
 #else
     // On P1, the route location is statically defined for the entire timer.
     PWM_TIMER->ROUTE &= ~_TIMER_ROUTE_LOCATION_MASK;
-if(pwmout_all_inactive()) {
+    // Make sure the route location is not overwritten
+    if(pwmout_all_inactive()) {
         PWM_TIMER->ROUTE |= pinmap_find_function(pin,PinMap_PWM) << _TIMER_ROUTE_LOCATION_SHIFT;
     } else {
-        MBED_ASSERT((pinmap_find_function(pin,PinMap_PWM) << _TIMER_ROUTE_LOCATION_SHIFT) == (PWM_TIMER->ROUTE & _TIMER_ROUTE_LOCATION_MASK));
+        MBED_ASSERT(PWM_TIMER->ROUTE & _TIMER_ROUTE_LOCATION_MASK == pinmap_find_function(pin,PinMap_PWM) << _TIMER_ROUTE_LOCATION_SHIFT);
     }
 #endif